Yes Scott, I pulled the headliner back, put a 1/2-20 nut & washer behind the factory plate and was lucky enough to get it tightened up after bending up one of my end wrenches. But it was definitely worth the work!
Bob: The GV comes with a new front yoke and I took my stock DL and the new yoke to a specialty shop and gave them the overall length I needed the driveline built. This was based on the GV requirement of yoke spline penetration into the tailshaft and distance to the pinion yoke. The shop dynamic balanced the DL and I installed in on the car. To my knowledge the tailshaft for the 904 is what you get-no choices. The actual change in angle came by the need to lower my transmission crossmember 1" to accommodate the GV unit.