Rear differential mount

[Radek]

My son's 88 90Q has been in the garage for the last couple of months, the rear differential is out, the rear subframe is out, so are the bumpers and it's getting an anti-rust treatment.  Now it's time to put it all back together.
We have treated the subframe with POR-15, looks good.  The question is now:  to replace or not to replace the subframe mounts?  They seem pretty solid.
The other question is:  what to do with the middle diff support (the one at the backof the diff)?  It's pretty much shot, the rubber seems ok but the shaft through which the bolt goes has separated from the rubber.  I checked pricing and it's outrageous!   Would anyone know if the bushing is available separately, without the aluminum mount surrounding it?  Or perhaps a way of reinforcing the existing one so it holds (I was thinking of adding rubber washers on the shaft on both sides so the diff would not move around?
TIA

Radek
91 V8Q 5-sp