Running 70-75 does not require a V-8. You need to start with the size tires you want to run, then choose rear gears that will allow you to run that speed at a comfortable engine RPM.

I have the rear from a '73 Chevelle wagon with 3.08 gears under mine. I can easily run 75+ with my six. A V-8 would easily do the same with those gears.

1955 1st GMC Suburban | 1954 GMC 250 trailer puller project | 1954 GMC 250 Hydra-Matic | 1954 Chevy 3100 . 1947 Chevy COE | and more...
It's true. I really don't do anything but browse the Internet looking for trouble...