S13 Auto->Manual Swap Question

[Shusaka]

I have read all the articles for this swap, they all say i will need a manual trans driveshaft, what is the major difference between the auto and manual driveshaft, i just picked up all i need to do my swap other than my crossmember and driveshaft, and was wondering if i can redrill the auto X-member and use the auto d/s or if the manual units are 100% necessary, i tried to search but with the new forum software, my search has been rendered temporarily unavailable

[rsagen]

the splines are different sizes and the shafts are 1 inch different in length. the auto drive shaft will not fit into the 5 speed transmission (too thick).