I need to change the bellhousing on my spare M47 before it goes into service. I don't really know anything about how things work inside the magic box that is the M47, but know there's some end play or preload or something that is supposed to be adjusted by the use of shims on the input shaft. If I'm not changing anything inside the transmission do things really change and necessitate measuring and possible changes to the shims?

One of the mounting ears on my spare's bellhousing is broken off. The car it came from drove fine before it was removed, despite the omitted bolt, but it seems stupid not to change the bellhousing when I've got a perfectly good one from my seized M47. I'd also replace the input shaft seal at the same time. I'm wary of getting in over my head here. To be frank, a running transmission with leaks and a broken mounting ear is preferable to one that neither leaks nor runs because I've messed something up.

Or, if there's a good writeup on how to measure and adjust things using those shims, I'd certainly be interested in learning how to do the job right. Any guidance from those well-versed in the intricacies of the M47 is much appreciated.