Yeah I dont know who sells em (Remflex brand header gaskets) but they have gotten regular constant reviews (enough that they would be my choice hands down). I would eyeball the flange & go from there if anything appears way out of line especially there between #5 #7. What I like to do is loctite the studs in the head & use a fine thread nut on the outer end & & I mockup ahead of time & trim the stud so there is just enough thread left to end up with the nut flush as any more is a waste & hampers flange fitment in tight compartments which doesn't sound like an issue for you just throwing that out there.