The 100hp axle it's self should be the same, but be careful it could possibly be in the same state as yours.
It's become increasingly common for the rear axles to rot out these days.
The hubs unbolt from the axle, so you can fit your drums to it, I'm not to sure converting to rear discs is worth it.
The rear disc brakes when fitted to different Pandas tend to become troublesome, binding, groaning and they don't really get worked hard enough to strip the rust, that forms on them off.
The Fiat 500 rear axle also fits, sort of.
It's a little wider in track, 50mm I think.
DaveMcT is the person you need, he fitted one to his.
Whatever you fit, make sure you remove the rust from it first and treat it to some better rust proofing.
Use the standard springs and shocks, 500 one tend to be softer.