I have a 81 camaro, 305 chevy stock except for a performer intake, and a holley 600, th350 trans, 3.08 rear gear, with 225/60/15 tires.
I'm trying to achieve the best mileage possible.

Don't know what kind of gas mileage you'd get.

I've got a 350 with a Q-Jet 4bbl and an Edelbrock Performer, and it's not too bad as a daily driver. But considering gas in CA. is now $3.00/gal http://www.nastyz28.com/ubb/mad.gif

12 mpg.

My pig '85 Olds Cutlass used to get 19 or 20 mpg, and that was burdened by massive smog equipment. IF the engine is sound and tuned up right you should not have a problem getting about the same. The deciding factor is going to be how good you are at tuning that carb.

Properly tuned Id say 18 hywy easy & 12-14 city.

My car got 17 hywy from Jacksonville to Raleigh. With a built smallblocck, 800 dp and 3000 stall with 3.42 gears.