I went ahead and took a chance and ran Felpro with orings on my truck. Made it 40,000 miles beating the HECK out of the truck. Multiple track runs, 100s of dyno runs, towing 15k up to the mountains on a race tune. Vgt, non-vgt, compounds, etc... Pushing around 650-700hp
I had to pull the motor because I had a random crank bearing go bad. BUT the heads did not even leak a little bit. Gaskets looked like new when I pulled them.
Before I pulled the motor I check for degas pressure on the dyno. I got the truck up to operating temps, released the pressure from the coolant heating up. Then put the cap back on and run a bunch of heavy loaded dyno runs. After about 1 hr of beating on the truck I went and pulled the degas bottle and there was almost zero presure, just a little tiny hiss when pulling it off.
Moral of the story... I had great luck and would recommend them to anyone