I had to fill the cross overs with epoxy because one of the darn things sprang a leak...LOL, yeah, all iron heads, heavily ported, so it is conceivable that maybe this had something to do with it, although the machine shop did a pressure test first and there was NO air coming out of the ported exhaust valve area.

Anyways, to answer your question, on top of this I used FelPro 1213S-3 intake gasket, which has the passages blocked off.

This is on a street car, but not a daily driver. Car heats up just fine (I only drive it in late spring, summer and early fall months), no issues to report.