Those old motors were designed to rur with some steep gears and I have one now with tall gears,it seemed to get better gas mileage with the 4.10 gears then with the 2.79s I have in it now so what can be done to make them run more efficient with taller gears. What I have is a 57 235 in my 37 chevy p/u and I took out the original 4.10 gears and 3 speed and replaced them with a 8 inch and a T-5,I know I should go with gears in the 3.40 range but one would think by not spinning the motor over like it did with the 4.10s would get better mileage but it did not.