I have 3.08 gears under my '55 1st GMC Suburban behind an SM420 4-speed and a basically stock GMC 270.
The rear came from a '73 Chevelle wagon and has the drum brakes from that car and disk in front using '73 Chevelle wagon when I ordered pieces.
It will run 75 but at that speed the steering and suspension don't inspire confidence. I need to rebuild the suspension if I want to run any faster than 70.
My motor is a little bigger and in some ways better than the 235 but I believe a similar combination would work for you.
