What's the difference between a '77 and an '85 carb? Is it worth swapping my low miles (45k) rebuilt '77 carb for a high miles (200k) rebuilt carb? Should I just swap the jets?
If I swap to the '85, how do I handle the fuel return? Do I need a fuel pump from similar vintage or could I use the top of the '77 carb or...?
I'm swapping to the '85 ignition at the same time if that makes any difference.

thanks,
david