David:
I can only speak from my experience. The covers for my car (1970 black vinyl, with NOS cloth inserts) came from Legendary, and they are beautiful. I am having a friend install them, and they fit really well (after repairing a bit of the old foams). As you correctly stated, it helps a bunch to heat them in the sun.
I ordered mine at the Nationals in Columbus, and they had a 'show special' price. They were still VERY expensive, but look awesome.
I hope the picture below helps you out - Give it a try! Good luck.
Tom