A while back I acquired a rally car that had a 180b rear grafted in. the job itself was rough (the car had rolled too, hence it eventually ending up here, it wasn't a project buildup or anything.

I have to say, given the weight of them , and the amount of stuffing around to make it fit in a coupe (and this never had to be street registered or anything, there's honestly no way I'd ever try it from scratch. There just isn't a large enough gain in handling to justify it, and it also ends up making the car heavier once you've welded in enough re-inforcements/pickups to mount it properly. If it came from the factory with one, then it wouldn't have to weigh more as they'd have designed it to suit, and there wounldn't be 'redundant' strengthening/pickup points for leaf springs.

You mentioned using it for strength, I think you are going to be better off with a bw diff conversion if that is the issue, and it'll 'fit' with a bit less hassle.