Originally Posted by Dan@Rapid-Ford

If it the same backend as the xr4i (which i think it is) I've been through this already.

cossy diff won't fit without fitting the whole cossy beam inc shafts and brakes

The diff he has in the car will have push in shafts so they will have to be changed to the cossie ones to match the diff then cv joints on the cossie are too big to go through the trailing arms and the car will have drums on the back so they will have to be swapped over to discs.

You could grind the trailing arms for clearance but it gets so thin you can almost see through it which I wasn't happy with then you have to mess about with the drums

and if you remove the driveshaft cups out of the cossie diff to use the push in shafts they won't reach far enough in to the diff to make both wheels turn.

in the end I fitted a complete cossie beam as I fitted a cossie engine and box aswell.

I then went through 2 welded diffs I cracked the casing on 1 underneath the crownwheel and the 2nd fired some weld through the rear cover fitted the 3rd and sold it to a local person to me who then sold it to pete RS specialist who sold it on ebay to a guy down the road to me

It was a fun car