Did you see Bill Verburg's post on the 915 gear options? He has some good information. I was interested in revising 2,3, 4 and maybe 5th:
They used to be
915/71
2nd 15:30 915.302.902.05
2nd 16:35 915.302.202.40
3rd 21:29 915.302.903.10
4th 25:27 915.302.904.15
5th 27:24 915.302.905.10
Much better ratios and better acceleration.
See Bill's post here:
http://forums.pelicanparts.com/porsche-911-technical-forum/539135-dan-here-your-transmissions.html