1970 Mustangs were mildly restyled. Headlight configuration reverted to a single seven-inch lamp on each side, this time inside the grille opening, Simulated scoops took the place of the outside headlights. The rear taillight panel was flat rather than concave and the taillights are recessed.
In the interior, a new steering wheel was used. The ignition switch was relocated on the steering column, as with all other domestic makes. The only optional interior was the Decor Group. It consisted of knitted vinyl or Blazer Stripe high-back buckets, simulated woodgrain applique on the dash, deluxe steering wheel, molded door panels with simulated woodgrain appliques, dual color-keyed racing mirrors, and rocker panel and wheel lip moldings.
High-back bucket seats were standard equipment on all Mustangs. The Sport Slats and rear deck wing were optional on all Mustang SportsRoofs.
The Shaker scoop was again optional on engines other than the 428 CJ-R. It was available with both 351s and also on the Boss 302.
The Competition Suspension was unchanged, except for the addition of a rear stabilizer bar, 1/2 inch on 351s and 5/8 inch on 428 engines.
The Drag Pack option, available only with 428 engines, came with 3.91:1 or 4.30:1 axle ratios. It consisted of an engine oil cooler, stronger 427-type connecting rods and different harmonic balancer /flywheel combinations. This option changes a Cobra Jet to a Super Cobra Jet.
All 1970 Mustangs with dual exhaust system benefited from a new exhaust system that used two mufflers mounted ahead of the rest axle, replacing the transverse muffler of previous years. All four-speed equipped Mustangs used a Hurst shifter.
While the 390 was dropped, a new 351 joined the line-up. The 351 Cleveland or 351C, available in two-barrel and four-barrel forms (250 and 300 hp) used cylinder heads which were very similar to those used on the Boss 302. The two-barrel engines used the so-called two-barrel heads which have smaller ports and valves. The four-barrel heads have the same size valves and ports as the Boss 302 cylinder heads. The 351W 4V was dropped but Mustangs equipped with the two-barrel 351 could either be a 351W or a 351C.
The Mach I was restyled, getting a revised grille that had two driving lamps. The NASCAR hood pins were replaced with twist- type latches and the blacked-out hood treatment of 1969 was replaced by a stripe arrangement in the middle of the hood, painted white or black. A complementary stripe was used on the rear deck lid, while the rear taillight panel got a honeycomb treatment. On the sides, aluminum rocker panel moldings with large Mach 1 lettering replaced the previous year's side tape stripes. Oval exhaust extensions replaced the quad arrangement on Mach 1s (and other Mustangs) with dual exhausts. Simulated sports wheel covers replaced the chrome styled steel wheels, but painted styled steel wheels were a no-cost option.
The Grande, too, was relatively unchanged. A half vinyl roof became part of the Grande package while in the interior, hound's- tooth cloth was used on the seats. The wire wheel covers became optional on the 1970 Grande.
The Boss 302 got a new tape stripe treatment that began on the hood (similar to the Mach 1), but then continued along the rear of the hood, down the front fenders and across the sides to the rear. Standard wheel size remained at 15x7; however, a trim ring/hub cap arrangement took the place of the Magnum 500s. Chrome Magnum 500 wheels, though, were optional but only on the Boss 302. The Shaker scoop was optional on the Boss 302.
Mechanically, the Boss 302 benefited from the redesigned dual exhaust system, the standard Hurst shifter, and the Competition Suspension which used a rear stabler bar measuring 5/8 inch. The engine got smaller intake valves, 2.19 inches versus 2.23 inches for 1969, which resulted in slightly better response. Aluminum valve covers replaced the chrome steel ones of 1969.
The 1970 Boss 429 featured a gloss black hood scoop, chrome Magnum 500 wheels that used a Boss 302 type center cap, the revised exhaust system and the Hurst shifter. Color availability was Grabber Blue, Grabber Orange, Grabber Green, Calypso Coral and Pastel Blue. Interior color selection was limited to black or white.
The 1970 Boss 429 engine was the 820-T version; however, it was fitted with a mechanical lifter ccamshaft and a more efficient radiator fan. Some engines were tagged 820-A. These were 820-T engines that had some minor emission system modifications. The 3/4 inch rear stabilizer bar was replaced by the 5/8 inch unit found on other Competition Suspension-equipped Mustangs.
A total of 499 1970 Boss 429s were built. KK numbers range from KK2060 to KK2558.
As with 1969 Bosses, all 1970 Boss 302 Mustangs had the consecutive unit number on the engine block for additional identi- fication. The Boss 429s had additional VIN numbers on the engine block, transmission and inner fenders.