covered amber bulbs that lit up at night in accordance with federal mandate. Surrounded by bright metal bezels, one might think the mid-February change to the rear reflectors was made to bring design harmony to the front and rear markers. But comparing the second-series rear reflector frames with the front marker frames revealed totally different efforts. A peek through the window of the local Lincoln-Mercury dealer solved the mystery. The same reflector was used on the 1968 Cougar, Comet, and Montego (see Fact No. 153 for more).
What’s behind the odd two-tone effect seen on the fender and hood graphics of the 1970 Boss 302? Fact No. 174 sheds light on the truth.
174 The entire 1969 Boss 302 side stripe graphic turned a pearlescent, reflective white when illuminated by headlamps at night, but the same cannot be said of the 1970 Boss 302 graphics. Expanded to embellish the horizontal surfaces of the front fenders and hood, only the vertical markings were rendered in the special reflective 3M tape. The remainder of the graphic consisted of solid, non-reflective material. The result is an odd two-tone effect under certain lighting conditions.
175 It’s difficult to imagine today, but non-Shelby Mustang buyers had to cough up an additional $54 for a tachometer in the 1967–1970 period, and this included Mach 1s and Bosses. This helps explain why so many 4-speed Mustangs today lack their original engine blocks. In a move calculated to control excessive crankshaft speed (and warranty claims), the 1969 Boss 302 was equipped with a standard Autolite ignition governor set at 6,150 rpm. Oddly, the 1969 Boss 429 did not share this vital ounce of prevention. But as 1969 Boss 429 customers began dropping valves, the 1970 Boss 429 adopted the 302’s ignition cutout unit, also set at 6,150 rpm. A similar unit was installed on 428 Cobra Jets but with a 5,800-rpm limit. Today, lost Autolite governors are available as faithful nonfunctional reproductions (they’re empty cases with no electronics to avoid legal hassles should a faulty unit trigger the loss of an irreplaceable numbers-matching engine).
176 On the handful of factory-built 1969 and 1970 Mustangs produced with the 351 2-barrel (H code) and optional Shaker hood scoop, Ford inserted a 1-inch-thick aluminum spacer between the cast-iron intake manifold and the carburetor base plate. Without the spacer, the low-rise, dual-plane, 2-barrel intake manifold reduced the total component stack height, causing the Shaker to sit too low in the hood skin cutout.
177 The Boss 429 1969 LID Mustang concept car (see Fact No. 128) broke the Boss 429’s 4-speed-only transmission recipe. While every one of the 1,358 Boss 429 Mustangs (859 in 1969 and 499 in 1970) sent power into a clutch-controlled Ford Toploader 4-speed manual gearbox, the LID Boss 429 was coupled to a heavy-duty C6 automatic. The LID Mustang existed in the heady realm of factory-built experimental machinery and cannot be included in the normal scheme of things. Its brief existence, however, must be acknowledged.
178 Ford’s desire to keep a lid on the raucous nature of big-block Mustangs led to the use of single cross-flow mufflers on all 1967–1969 factory dual-exhaust systems (including Shelby and Boss). Although they were often discarded in favor of completely separate piping and a dedicated muffler for each bank of cylinders, faithful restorations must include the somewhat restrictive canister-style muffler fitted sideways between the rear axle and gas tank.
Mustang dual-exhaust systems were improved dramatically in 1970. See Fact No. 178 for more.
179 Performance fans cheered in 1970 when Ford eliminated the restrictive cross-flow muffler and switched to more efficient true dual-exhaust plumbing under all high-performance Mustangs. Even though advertised horsepower ratings were unchanged, the reduced back pressure certainly increased power and greatly improved the Mustang’s “street credibility” thanks to a more aggressive burble at idle and a throaty roar at full throttle.
180 The amount of power gained from the improved 1970 straight-through exhaust system strategy depended upon the engine. Conservative powerplants such as the 300-hp (rated) 351 Windsor and Cleveland 4-barrel likely saw an extra 5 to 10 hp. The 335-hp (again, rated) 428 CJ and CJ-R appreciated the improved plumbing even more and responded with an extra 15 hp. But the Boss 302 and Boss 429 saw the greatest gains. Born to breathe and rev (the 302 was fitted with a 6,150-rpm limiter, because it was apt to spin high), the 1969 transverse exhaust was particularly stifling. Again, although no advertised claims were made (Boss 302 = 290 hp, Boss 429 = 375 hp), the true duals are said to have been worth 25 to 30 hp on these rev-happy stormers.
181 Before the Fox body Mustang gave it a high-performance image makeover as the 5.0 HO, the 302 small-block was marketed as a bland work horse. There were two exceptions, the mighty 1969–1970 Boss 302 and the often overlooked 1968-only J-code. While the Boss 302 truly was a detuned racing engine with unique canted valvehe-ads, four-bolt main caps, and numerous ultra-duty parts, the J-code arrived in mid-1968 to fill the spot vacated by the A-code 225-hp 289 of 1965–1967. Rated at 230 hp, the J-code inhaled through a single 441-cfm Autolite 4300 series 4-barrel carburetor but shared the same single exhaust system as its 210-hp 2-barrel 302 cousin (engine code F). The Boss 302 and J-code 302 stand as the only factory 4-barrel 302s prior to the Holley 4-barrel 1983 HO edition.
182 The lone exception to the J-code 302 Mustang’s single-exhaust-only penance came when it was combined with the GT Equipment Group. Then, fashionable chrome tips emerged from both sides of the specially stamped rear valance panel. Advertised horsepower remained at 230.
183 The demise of the spirited solid lifter K-code Hi-Po 289 at the end of the 1967 model year forced Shelby Automotive to adopt the new 302 for the 1968 GT350 Mustang. Naturally, the A.O. Smith assembly team started with J-code 4-barrel cars, then added cast-aluminum single 4-barrel intake manifolds, finned (black) Cobra valvecovers and a mild vacuum-secondary 600-cfm Holley 4-barrel under an ovoid cast-aluminum Shelby air cleaner. The standard J-code iron exhaust manifolds and Mustang GT-spec dual-exhaust system remained in place, although Shelby added a new pipe-within-a-pipe dual chrome-tip configuration. The Shelby top-end engine upgrades bumped power from 230 to 250 hp. With 1,657 built (1,253 fastbacks, 404 convertibles) the 1968 GT350 was the only Shelby Mustang, but the 302, and at 250 hp, the least powerful of the breed.
184 Many of the first 1968 GT350s delivered to customers lacked the Shelby intake and Holley carburetor due to delays in the emissions certification process. Afflicted cars received the special Shelby valvecovers and air cleaner but retained the clunky Ford 4-barrel induction system. Vouchers were issued with these cars so that (after the certification delay was ironed out) their owners could have the Shelby inductions installed at a later date, free of charge, by the retail dealer. Surprisingly (or maybe not, considering the GT350s de-emphasized performance theme), many customers ignored the Shelby alert and never returned for their upgraded parts.
185 Restoring some of the performance lost during the 1968 302 escapade, the 1969 GT350 took full advantage of the 1969 arrival of the 351 Windsor on Mustang option sheets. Fundamentally similar to the 221, 260, 289, 302 small-block engine family, the 351 shared the 302’s 4.002-inch bore diameter but received its extra displacement via a taller engine block (9.480 deck height) with which to accommodate its 3.50-inch stroke. Sharing virtually identical Windsor-style (inline valves) cylinder heads with the non-Boss 302, the 351 Windsor was offered with a single 2-barrel and 250 hp (engine code H) or a single 4-barrel and 290 hp (engine code M).
186 For the 1969 GT350, the A.O. Smith conversion workers (who’d been handling the job since Mustang’s 1968 model
