Loosen all 4 bolts holding the remote shift to the diff housing by a couple of turns so you can rock the motor.
Somebody has stripped the steady hole in the block, drill the steel steady bush and bracket out. It's much stronger now.
But I think you will be disappointed with lurethane bushes. They transmit vibes to the body, and don't last in this application.
We put them on a mate's 1108 Mini with a remote box and they were rooted in 6 weeks.
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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.