75A is indeed stiff for motormount rubber. (for suspension rubber like bushings its normal, but the motormounts of course have a very diffenent type of load).
The transmission mounts are generic 'type A' (threads at both ends) vibration dampers.
I don't know the exact size anymore, maybe 30x30mm M8? I think they were shore55A or so. And that's already noticeable stiffer than the stock ones.
It's been a very long time since I did this mod, over 8 years ago I think.
I used 1 or 2 rings to match the exact height to the stock mounts:
(they are a little bit more narrow than the stock mounts but already way stiffer)
