does anyone make a gasket that is close to original thickness? the ones i've seen are thin and cheap.

I would think you could still get originals from GM, as the '70 lenses are still available.

I just went through the same thing. How hard would it be for them to cut those gaskets out of material that is actually thick enough to do the job that it is intended for? I contact cemented two sets together to get them thick enough which worked, but I couldn't sleep at night. I finally found a good used set on ebay.

Also, don't use laquer thinner to clean the original gaskets. I soaked mine in it and ruined them that way.