i have a 1988 diesel E350 ambulance with posi 4.10 gears, i want to go to a 3.31 gear ratio, i was given a 1979 E250 rear end 3.51 non posi gear ratio,
i want to end up with a 3.31 posi rear end using the stuff i have, can i buy 3.31 ring and pinion and use in any of these rear ends or should i find a different rear end, i think i have a dana 61 in the 88 e350 and a dana 60 in the 79 e250, how can i verify these rear end (no tags plate on diff) i want better gas mileage