I am giving up with the 700r4 tranny, I've got nothing against it but they just dont last with towing and other assorted abuse. Have bought a complete 79' 1/2 ton pick-up with the SM465/205 tranny set up to transplant into the Blazer. As I am losing the overdrive gear I am trying to figure what will be a good axle ratio to use to keep the engine rpm's sensible on the highway. I am running 31x10.5/15 tyres and have no wish to go any bigger, I would prefer to change the gearing than lift the truck and fit larger tyres. Any advice/suggestions would be appreciated.