Can anyone tell me if they (or your mechanic) had to modify the gearset (possibly grind it) to have it fit without clearance issues with the carrier?
My supposed to be supplier said his shop couldn't get a 3.73 gearset onto a Mustang w/o grinding it down. An emmsions trap set by ford according to him. (could shorter gears really have us fail smog due to higher RPM testing?)

I am almost certain it's BS, but knowing a ton of people here have regeared their car's, I can at least feel good at getting some back up that a gearset designed for our 7.5" rear should be good to go out of the box.

 

Find another mechanic. Find gears that fit.

 

He wasn't going to install it, but I think it was a slick way to get out of suppling the parts for cheap. Can't tell. (looks like Auburn and Richmond are out)
Either way I'm just going to order online from a reliable source.

 

Wise man.