1) The rear end all fits together fine. The rear axles fit perfect into an SS. The WRX rear axles do NOT have circlips on them, as the clips are internal in the diff. I swapped the WRX diff studs for my SS ones, because they are shorter and made installation MUCH easier. You will also need to use the SS pinion flange, since the bolts on the WRX driveshaft are evenly spaced around the flange.
2) You can simply unscrew the speedometer base from the SS tranny and screw it into the WRX tranny.
3) You will need axle stubs to be able to use your stock front axles. My WRX tranny was from a sedan, so the front CV axles were too long to fit the SS. I took both axles apart, and there is no way to make a hybrid axle without other parts. I ordered the stubs for a 2004 STI. They have the same end that plugs into the tranny, but provides the splined nub sticking out of the tranny so you can attach your axles.
The part numbers are:
2x 905190007 Spring Pin $3.42 (For the Inner CV->axle stub)
2x 38415AA110 Shaft Axle $37.99 (for an '04 STi)
2x 805329010 Circlip $0.43 (retains the STi Stub in the diff)
1x 806730041 Oil Seal $3.60 (for the axle stub)
1x 806730042 Oil Seal $3.60 (for the axle stub)
That's about it so far. I just got the rear end in tonight, but I need to wait for the axle stubs and stuff to arrive before I can get the tranny in the car. Until then it's back to driving a POS Taurus......
