I did some searching but couldn’t find any useful information about converting a 266 to 268 top end. Anyway my question is this. For those who’ve done it, what gasket did you use between the cylinder and air filter housing? The one that seals around the insulator block. I have 266 and 268 gaskets but it looks like the 268 one may not work. 266 gasket doesn’t seal completely around the 268 insulator block. Thoughts?