does it dive to the right or just kinda drift that way? Rear brake adjustment has some sway over drift. Dive is more likely front caliper hanging or possible a hose, gm hoses are notorious for the inner tube pinching and acting like a check valve.
Current tires no wear are 31.7" in diameter.
If you get true 33" you will drop @120 rpm in high gear. True 35" will get a @220 rpm drop in high gear. So @2300 at 70 with 35's.
2nd gear starts might still be possible. That's 12.2 to 1.
What size tires are on it now?
I had a 77 with sm465 33s" 4.10s
I used a tuff county ez ride 2.5" lift front and rear springs tuff county shocks. Only a slight rub front edge of fender. 8" wheel forget offset.
Well is wishful thinking. New house 2 mortgages for a few months till I rent my Kommiefornia house. But any CK5'ers want to grab it go for it. I thought it was neat and I do like the 78 Bronco, round head lights.