Sanderson and I had a "discussion" about this very subject. They are full of c@#p with the RTV. Exhaust flow can reach 1200*F on occasion and that RTV is not acceptable. As far as flat - they build up the flange with MIG weld then grind it - and flat, mine sure weren't!!! I looked at the Fel-Pro gaskets, but the holes were too small for the GT40P heads so ended up with these from Earls - not cheap, but a quality part: http://www.summitracing.com/parts/EAR-29D03AERL/