I also like the FelPro header gaskets, using them both on my aluminum headed 347 SBF, and my iron headed 427 and 428 drag engines. On my FPA headers, on the 428 in my 59, I used the supplied FPA gaskets, I am going to use the FelPro header gaskets now with the new TFS heads. To me, unless you have headers that you can install with the engine on the engine stand, using silicone on the flanges of the headers , with the engine installed, seems like a great way to just smear RTV all over the heads, header pipes, shock towers, and your hands. And unless both the head surfaces and the exhaust flanges are really straight, I can`t see the RTV being able to seal any voids with high temperature, high pressure exhaust gases.