[klownkar]

the 350 in my 70 chevy with a performer cam and manifold, and a 600 carter afb with a manual choke got right at 15 mpg consistently on the highway. It was bored .030 over and had mild compression. I think that that is about as good as you will bet unless you go with a 700-r4. I have to agree with junkyard, anybody claiming more than that with a carb is blowing smoke and doesn't know the math.