1970 GMC C/M Series 4500-6500 Engines

[Bob B.]

I think you are confusing 2 different trucks. The 1966-1969 medium duty GMC 4500-6500 trucks were the E series. The E series used the same cab and hood as the H/J series, though the fenders on certain versions were narrower. In 1970, the E series was replaced with a GMC version of the Chevy C/M series medium duty. The E series was available with the Chevy straight 6, GMC V-6, or Toroflow diesel. The 1970 GMC C/M series was available with Chevy straight 6 and V-8, GMC V-6 and Toroflow, and the Detroit 4-53. The GMC V-6 was not available in the Chevy C/M series before 1970. The 1966-1969 conventional GMC school bus chassis was the S series, and it was basically just a cowl version of the E series.

Yes, from 1970 through 1974 both Chevy and GMC medium trucks were available with Chevy and GMC gas engines. Toroflows as well.