Well, this probably won't help a whole lot, but I went from 3.08 to 4.56 in mine and it was absolutely AWESOME!!!!!!....highway driving sucked, as well as mileage, but it was a Mustang buster with that gear in it..now I must say that it also had a "lincoln lock" differential, that was probably one of the more dangerous things I have done, but it was VERY VERY quick...............just my 2 or 3 cents worth
oh yeah, the engine was a 355.....10.25 to 1..........041 heads...........294-.525 solid lift cam......Holley 750 DBl pumper.Victor Jr. and headers..........