This is pretty interesting reading. I'm leaning towards a Sherwood dual outlet manifold with a Mk5 clone that I currently own as the backup to an Aquamaster. It'll be an interesting project I'll just be fiddling along with all summer getting it together. One thought I had was to use a bare harness with no horsecollar to keep the appearance of vintage, but use my drysuit for buoyancy. Does anyone do this?
Yes, it has being done many times. The Poseidon Unisuit actually predates many BC's. I don't have much experience with that particular dry suit since I grew up diving in the Caribbean. I do own one of them now.
A laminate type suit may actually work better since you don't have to compensate for the neoprene compression. My normal dry-suit is neoprene, but here in Maine most of our dives seldom go under 40 ft.