71 GMC Longhorn, compatible engine and transmition

[JerryIndy2112]

Hey, all.

I bought this 1971 1 ton longhorn GMC pick up. I am meaning to restore it and use it as a truck. It has a 402 BBC in it. I am in the process of getting some tires on it. But for the long term, the engine burns oil and the transmission does not seem to shift up to highest gear. RPM's seem high at 35 mph. Current tires are so bad that I have not tried to open up on highway or open road. There is a lot of work to do on this truck. Body, engine, transmission, door hardware. But at least most of the damn shag carpet it gone now, lol. I talked with a guy about a fresh rebuild of the 402, but is it worth it? Will a 427 or 454 fit in its place without major work? How do I identify the current transmission and even the 4 barrel carburetor? I am new to restoration, but needed a hobby. I worked on cars back in the early '80s and even rebuilt a 350, but it has been years. Can I get a bit of info on these issues to help steer me in the right direction?

Thanks Jerry