I bought this belt a few years ago and was told it is for a 72 455. The Gm part # is 9433750 GG. $55 shipped.
Fits 70 and 71 as well standard 455. Is 49” where Stage-1 use a 50” part 9433752. They both should work. They must have wanted a Stage1 to spin slower. The Buick parts list shows the 752 belt as being for GSX which makes zero sense? I bet they meant Stage?
There's one on ebay now, Joe. That's about right from my experience, $50.-65. if you're lucky enough to find one.
Joe, at least 3 companies (Gates, Goodyear, Dayco) made the belts and hoses for GM cars. Your belt is a Dayco, in just different packaging. A true assembly line 70 GS 455 belt would have been a cloth construction 7/16" with raised, embossed numbers. I actually like the printed ones with a bit more modern construction better.