[Richard]

My 72 I am currently working on originally had a 350/350 combo with 31" tires and 3.73 gears. Little higher RPM than I liked but drivable. 10 mpg all day long empty or loaded. 33's will drop the rpm a bit should be fine. Look up rpm calculators and input your info, have used the Spicer one many times. Add about 200 rpm to result for non lockout trans and it should be pretty close. As said all non OD transmissions are 1:1 in final gear, so expect about 200 rpm higher.