I think the best differential to buy is whichever one you are most comfortable with. The statements about the Quaife needing to be machined are somewhat misleading, the need to be machined has nothing too do with the differential. Ford built the transmission with two different size carrier bearings (17.5mm & 19mm). If your transmission was built with the narrow bearing and you buy the Torsen you will have to machine it as well. I would also tell you that increased torque bias isn't going to change the fact if your car is capable of spining both front tires it will do so with either the Torsen or Quaife. My opinion is whichever you buy will be a big improvement over stock. Personally I have the quaife, I drove from Texas to Michigan to have Terry Haines do the install(no machining)and I am very happy with it.
