I am about to swap my 3.55 for 4.56 gears. My spider gears need changing too. I do not have limited slip but want to install it. I am intrested in the Ford Limited Slip because it is not as aggressive as the locker i was going to get. The problem i have is i do not know the correct name of the LS and dont know any part #'s for it. I need some input on this matter b/c i trust the fellow f150 owners rather than the local shady 4wheel drive shop.

 

This might be it

http://www.oem-car-parts.com/default...ord-parts.com2

It is a genuine Ford parts website. They should have what you're looking for at a reasonable price.

 

Factory, OEM part# on 31-spline trac-loc should be: M4204f318. I have seen this OEM trac-loc in Jeg's catalog. You might want to do some shopping--might save some $$$?