[54belair]

This combo should work for you-----unless you are wanting to jump from light to light. This combo will give you ok city driving and decent mileage on hiway driving.
This is the combo I have in my build, spent some time crunching the numbers---it will work. Now, with that said, I also have to say you need an engine that will produce low end torque instead of high end H P. If you have a cam that produces power in the higher ranges, then your stop and go will suffer. I went with an old style "rv cam"---something that starts pulling at about 1200-1500 rpm. If youre cam gives you a power band starting much higher than that---You might think about the 3;42's
Im old and don't give two hoots about a lopie cam, the stock and the "rv" cam will give you the low end to work with the 3.08's (I know you said you had an M20 so Im just throwing in this for fyi----If you could come up with a borg-warner t 10--------that would work even better, it has a 2.64 first gear opposed to the M 20's 2.56)