Plymouth regained its third place ranking in 1970, the best the brand had registered since 1959. The backbone of its 7.4 percent sales increase was the new Valiant Duster Coupe which registered an astonishing 217,192 sales. Changes to the 1970 Plymouth Road Runner and 1970 Plymouth GTX lines involved new grille, hoods, fenders and rear panel.

The year 1970 was the pinnacle of the muscle car wars. The 425 bhp, 426 cid Street Hemi was king and the Road Runner Superbird ruled NASCAR’s superspeedways. Even so, Road Runner sales dropped 50 percent this year, with only 15,716 Coupes, 24,944 Hardtops, only 824 Convertibles. There were also 1,920 Superbirds – one for every two Plymouth dealers. The Superbird closely resembled the Dodge Charger Daytona from 1969 (500 built), but the two are distinctly different.

The GTX lost its convertible this year and only 7,748 Hardtops were sold. The base engine for the Road Runner remained the 330 bhp, 383 cid V-8 with optional 375 bhp 440 cid V-8 for an extra $131, the 390 bhp 440 V-8 “Six Pack” for $250 more, and the dual-four-barrel 425 bhp 426 Street Hemi V-8 for another $831.40. Base gearbox was now a 3-speed with a 4-speed for $197 and automatic available for an extra $227.

The GTX featured a 375 bhp 440 V-8 as base motor with a 390 bhp 440 “Six Pack” available for $119 extra, and the 425 bhp, 426 cid Street Hemi for an additional $711. Automatic transmission was standard on the GTX with a no-charge 4-speed. Air conditioning was not available with high performance engines.

Road Test tried out a base Superbird with a 440 V-8 and managed 0-60 mph in 5.8 seconds and a quarter-mile in 14.26 second at 103.7 mph. A Hemi Road Runner managed 0-60 in 5.6 seconds and the quarter-mile in 13.7 seconds at 106 mph.

Popular Road Runner and GTX options included air-conditioning ($357), Road Runner stripes ($27), blackout hood ($18 for Road Runner and GTX), AM/FM stereo tape ($196), vinyl roof ($79), air-grabber scoop ($66 but standard with Hemi), front disc brakes ($28), heavy duty Sure-Grip differential ($146), Super Trak Pack with 440 or 426 V-8s ($236), Road Runner bucket seats ($100), and tachometer ($50).

Plymouth offered 27 mostly metallic and high impact colors, and seven interior shades. The colors and codes were Platinum (A4), Ice Blue (B3), Blue Fire (B5), Jamaica Blue, (B7), In-Violet (C7), Rally Red (E5), Lime Green (F4), Ivy Green (F8), Limelight (J5), Vitamin C (K2), Burnt Orange (K3), Deep Burnet Orange (K5), Sandpebble Beige (L1), Moulin Rouge (M3), Frosted Teal (P6), Scorch Red (R6), Sahara Tan (T3), Burnt Tan (T6), Walnut (T8), Tor Red (V2), Alpine White (W1), Black Velvet (X9), Lemon Twist (Y1), Sunflower Yellow (Y2), Yellow Gold (Y3), Citron Mist (Y4), Citron Gold (Y6). Interior colors included Blue, Green, Tan, Charcoal, Burnt Orange, and Gold. Vinyl roofs tended to be White, Black, Green or Tan.