[DanEC]

Lippy - sorry to hear this. Putting one of those in by yourself from the topside is a real job. If it is the length of the transmission bearing retainer, I think rather than using a spacer, I would remove the retainer and shorten it enough to clear. The length is un-important contingent upon it being long enough to support the full stroke of the throw out bearing.

From every thing you have described it almost is a sure thing it has to be the bearing retainer hiting the back clutch disc hub. It sounds like removal of 3/32" from the length will do it and that does absolutely no harm to anything else.