Depends how much power you're looking for and if you want an in-tank or external.
Personally, I'd go with an OEM Denso pump (something like a Supra pump) on a hanger if I was doing an LS swap, but it won't be cheap and will take some fabbing.
Externals will be noticeably noisy but if it's...
The Caddy manifolds will more than likely still interfere. If they do on an 80 frame they probably will on a 70 frame. The Hookers are worth the shot. Maybe @SNLC can do a couple quick measurement for you on my setup with those Hookers.