most of this is stuff you'll have to fabricate, you'll need to weld mounts on the diff, and make your own mounting points on the body. It'd be a good idea to take it to an engineer to get the welding done and the geometry sorted out properly so you can get it certified.

The arms could be sourced from something else, Toyota sprinter or Series 1,2,3 RX7 would be good.

I always hang my suspension off the cage, it's the strongest I can make it, and it's only slightly illegal in the 'non-spaceframe' categories...