Good point. With most things related to vintage sleds I would prefer OEM stuff.....thing such as pistons, etc. But a rubber item is a whole different ball game. Even if they are sealed up in a plastic wrapper, they are nearly 40 years old
I have had great luck with Winderosa gaskets and seal kits in all my sleds....literally all of my sleds listed below have Winderosa crank seals.
But, I know some very knowledgeable people on here have had trouble with them, mainly with the head gaskets leaking.
I'm going with Winderosa seals on the new Invader that I picked up, but I may tear into it enough to look at the top end, then I would probably prefer OEM gaskets for the cylinder base and head gaskets.