For my 1950's Slingerlands, I use Aquarian American Vintage heads. Medium on top, thin on bottom.My options are limited by the size of my older shells. American Vintage heads, which are oversized to fit old drums, may be the only mass-produced plastic heads that'll fit.
I've got Aquarian American Vintage on my '65/'66 Ludwigs, and I love them. Medium weight on top and bottom. They give a nice, warm, natural sound -- like a warmer, rounder Ambassador. And the off-white coating looks nice. As has been pointed out elsewhere, if you need an oversized head to accommodate larger vintage shells, make sure you get the American Vintage series. Aquarian also makes a series called Modern Vintage, which are not oversized.
I've heard that Ludwig heads may also accommodate oversized vintage shells, and have the added advantage of being pretty inexpensive, but I haven't tried them.