ok i have a 66 fury 2 sedan it had a 318 poly in it i swapped it out put in a 383 with a 727 got it hooked up runs great i got new exhaust on it and everything now i am trying to focus on the rear end it does not have posi or "suregrip" only one wheel spins i want both to spin now so what differential do i look for to change it to sure grip i want to find one at a salvage yard im 16 and i dont know where to start

 

First identify what axle you have. The first way to find one is turn one wheel flange and the other should turn same direction, if it turns opposite it is an open (non-limited slip) differential.

 

Finding one at a salvage yard may be tough, as they have not used the 8 3/4 rear end in many years. Not impossible