4 speed crossmember

[edison1970]

Does anyone know the difference between 70-72 and 73-74 crossmember?  The reason I ask is that I  noticed my car was getting hard to shift into 2nd gear. Looking under the car, I noticed the two shift rods were rubbing the frame. I messaged it a little but it still rubs. I'm thinking the transmission mount is toast. Since my car was assembled with a host of different year parts, I'm not sure which rubber mount to get. Any help would be appreciated. 
Thanks

[anlauto]

The four long bolts that mount the crossmember have different hole spacing and the overall length is different. The center two holes are the same, it's on the longer 70-71 piece that the outer holes are further apart then the 73-74 piece.

[edison1970]

So the rubber isolator is different between the 2?

[anlauto]

Nope, that part is the same

[Chryco Psycho]

Energy Suspension makes a Poly insert for the mount as an option .

[edison1970]

Thanks for the replies. One more question.  Is there supposed to be a 1/8" shim between the mount and where it bolts to the tail shaft? My friends 1970 Cuda and Challenger both had one. I've never seen one in any of the cars I've had.

[Chryco Psycho]

Most I have seen have retangular "washers" under the mount due to the Oval holes in the mount but have not had a shim above the mount althoug that can help with driveline angle .