I did a search but cannot find to much info on the swap. Putting a 421 in my car and I know the 9 bolt is going to break so I have been reserching rear ends. Basically want a something like a limited slip but with strength. Dont want a spool since its a street strip car. Here is what Im looking at. A strange dana s60 35 splines with an Strac differential. Id like to hear opinions on this. Things I know. It is heaviest of the three swaps. 9inch , 12 bolt and dana. From all my reserch it is only supposed to be 10 pounds heavier than a comparable 9 inch with regular housing and iron case. Thing is to match the dana60 and use a fab type 9inch with hybrid aluminum case and 35 splines the price really gets up there. Plus I know its trivial, but its a ford,cmon... Been told strange will mount my 9 bolt brake backing plates and heard they fit. and it has the mount for torque arm cast in the case. Heard of guys running the 9 inches and 12 bolts with the torque are adapter mount having tunnel clearence problems, have not heard of that about the dana. Best thing is the price. Very resonable compared to the other two. Also have read that when you run a fab 9 you need to run that man. torue arm. Want street manners and would like to use poly mounts instead of the noisy shperical ones. Anyone got any input on these. Was talking with Midwest as they seem the go to for the lt and ls crowd. Thanks