Be aware that a Chevelle/Nova etc rear end would be 5 lug vs the 8 lug front end on a 3/4 ton truck. Providing that your GMC has the same corporate rear end as a Chevy of that era you could obtain a 4:10 replacement from a 67-72 GM truck. That would also work well with the 700R4 transmission. You could still attain highway speeds and still use it as a truck.
Fred
