I've been doing a diff swap the last couple of days, but I don't understand your Question. As far as I know, they only go in one way.

 

I put a R200/ 4.11 in my 73 and I keep getting a grinding sound and its dragging on the engine, like something is binding up. The only thing I can think of is that the Diff is not far enough back and it's pushing the drive shaft too hard into the transmission.

 

I'm swapping an R-200 out for an R-200 3.90, in a 75 280, so I'm not sure I can help. Sorry, I wish I could.

 

Bill,
If you are asking about the diff mount in the front then, the long part goes towards the front of the car, i.e. the single bolt on the mount is in front of the two on the diff. However, if you had this backwards, you never would have been able to get both the front and the mustache bar to mount. Your mustache bar is now located BEHIND the rear risers..Correct?

 

Mustache Bar Behind the Risers? As in on the Fuel Tank Side?
And the Risers being the 2 Flat Plates that come down to the rear control arms?

 

I think that is what he is saying. If you replace the R180 with the R200 the mustache bar goes on the opposite side of the risers and I think the end bushings bend the opposite way. When it gets done it should look like the installation on a 280.

 

Thanks! It now Works!!!