Does anyone know of a Limited Slip differntial i can use in a 77 F-150 2wd?

 

There are a number of aftermarket manufacturers of limited slip/posi-traction units for the Ford 9" rear end in you truck. Ford also made a unit refered to as "Trac-Loc" for these trucks. Go to Jeff's Bronco Graveyard, Early Bronco Restoration Full Size Bronco Restoration Classic Ford Bronco Parts For Sale, you can get some ideas there.

 

If you want to go with a locker you could get a power trax locker. Every thing fits in the stock diff case. locks when on the gas and unlocks when coasting around turns. Friend had one in his ranger, worked great, did not handle to bad with it. Thinking about getting one for my F-150.