I have some very nice spares that came out of the 901 transmission from my '66 912. This transmission has 85K miles on it, the bearings are practically new with less than 10K miles (maybe as few as 5K miles) from a previous rebuild that did not fix an unrelated problem (pinion depth). These are advertised on Pelican - everything is compatible with 914 transmissions except for the intermediate plate which fits early tail-shift cases. There are several auctions here, so please ping me if you have any questions about specific items:
M, S, X matched pair gear sets, $200 ea or $500 including shipping for all 3: http://forums.pelicanparts.com/porsche-911...sets-m-s-x.html
Intermediate plate with both bearing sets, races, 1&2 (A, F) gear sets, main shaft, $450 O.B.O: http://forums.pelicanparts.com/porsche-911...ears-450-a.html
Pinion shaft with roller bearing, $100 O.B.O.: http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/608021-901-pinion-shaft-roller-bearing-100-a.html