£25 delivered these will have to be - only got x2 at the moment as I want to get a good feedback from first x2 that try fitment before everyone wants one.
I don't know if you would need longer bolts - you might do but I would think the std ones would easily hold. Like I say looking for fitment feedback from the first one or two to confirm this but people have fitted these in the past with std bolts - thicker than std but not sure by how much.
PTFE gaskets are used by many motorsport companies and have been for years... we have seen positive results when we have been asked to make them for other cars - generally hot hatches - i.e. clio williams, 172, etc.