I've found 2 gasket sets for the 400. Fel-Pro ks2614 and fs8364pt. They both come with permtorque head gaskets. The gasket in the fs8364pt is .039 thick and I can't find info on the ks2614. Wher can I find more info on these sets? the fs8364pt is double the price of the ks2614. is it worth the difference on my application?