If you follow BaT, you’ll know what I am thinking…
This has been covered many times, I would not start changing the back plates and seals. A complete gearbox with overdrive might work though, especially with the right bellhousing and starter (mixing 4.2L and 3.8L parts can turn into a mess). Converting a 2+2 with an auto box with a setup like that can be very motivating, IMHO.
In my ex S1 2+2 the gearbox, bellhousing and overdrive all came from a S1 XJ6 and thus the gearbox top cover, shifter stick and pivot lever needed to be changed to get the right stick in the right position.