No issues with the JTR piece, couple of install pictures here. I created larger plates inside the floor that go up the side of the tunnel.
here's some install pictures.
http://www.jhoski.com/automotive/350z-project/350z-phase-3
Try PST driveshafts. They do a lot of circle track and custom hotrods. My custom built steel shaft with Powerglide yoke, 1310 u joints, and no diff adapter (already had the JTR adapter) was $170 delivered.
http://www.pstds.com/