When we put our XJS on the lift, the rear subframe almost fell off the car!
In my opinion, these stock mounts look like a really unsafe way to mount a suspension crossmember to a vehicle. Has anyone came up with an upgrade for these? They don't even seem to have any bolt that goes through them, so when our engine swap is done I'm worried about the mounts breaking even if they were replaced with new factory ones.
If I can't find anything I might just modify the stock mounting brackets to accept some Energy Suspension transmission mounts instead. They cost about the same as stock, but are interlocked inside so they can't separate.

 

I ordered 4 new stock mounts today, I guess we'll give it a shot and see how it holds up. If I have a problem with them again I'll make some type of upgrade for it.