Hi, i want a little more oomph to my 1966 mustang and i realized gears are the way to do it. I would like to change to a limited slip differential and i would like to know what all should be accounted for during the swap. Will 3.73 gears hurt mpg even considering i dont drive it even 50mph often, as it only brings me to school and work everyday. Most driving is 35 to 40 mph so i doubt it would do much difference, i hope. And for the swap, can you just buy the limited slip unit and install it with new gears? I think its as simple as that but i like to be sure before i dump a couple hundred on a part. I was thinking of buying a so called "8 inch Posi" unit from jegs or so for round 350 to 400 dollars. Will this just do the job? Im a virgin to these rear ends:hihi: so someone please enlighten me. Thanks in advance.