any of you running a 350/ turbo350 with a highway gear in there hot rod? getting ready to put a new 350/290 in my hot rod i have a turbo 350 in it now with a 2.79 gear wondering how the gas mileage would be? i got an old 283 2bbl in it now get sometimes about 20 mph now. getting ready to head west this summer, dont really want to change to an overdrive but might have too. any thoughts?