For what it's worth, in building my car we used a BMW M1 transaxle- that is, a ZF5DS25/2. This transaxle is oriented "properly" already as it comes from the ZF factory. By properly I mean as we GT40 enthusiasts define it. ZF units in Panteras are inverted from the GT40 position, which works fine as long as you do the internal modifications, not limited to flipping the ring gear over. There are some oiling issues too from what I gather.
The BMW M1 is a LHD car. What this meant with my unit, because 1149 is a RHD/RHS car, was that the transmission had to be modified so that the shifter could approach the transmission from the right. Other mods included safety-wiring the ring-gear bolts and replacing the BMW M1 top plate with one, made I think by RBT, which includes the transmission mount to the GT40s monocoque.
For most of you, who are using standard Ford clutches, as did I, the issue may be how much clearance there is between the chassis and the bellhousing to permit the shift linkage to travel through. We may have to make some mods there. 1149 has a Mark I monocoque and space is not plentiful in that area. Most original GT40s have a smaller bellhousing with a multiplate AP or Tilton clutch. Not what I wanted and not what you want either, frankly.
Bob Byars at Precision Proformance did the mods to my ZF. So far so good, although we haven't run it very much. Another interesting tidbit- the input shaft spline on the BMW transaxle appears to be the same as on a small-block Chevy clutch disc. Imagine that. /ubbthreads/images/graemlins/grin.gif