Mileage
 

Is there a big difference in MPG on 3.27 vs. 3.73

As long as you stay out of it, everyday city driving should be the same. Highway cruising will decrease by about 2mpg.

Gas mileage
 

I don't know about your gears specifically, but I can tell you that going from 3:fifty-whatever to 4:10 on my '03 5 speed cost me 1 mpg. A small sacrifice to make for greatly improved performance, and a lot more fun. :D

Thanks for the info you have a really clean looking stang

no problemo