Blocking the heat crossover, IN the head.

You could always get an intake that doesn't have the passageways cast into it. Edelbrock Performer, Weiand Stealth, & Edel. Air-Gap all come to mind.

True, but that's mo money. I already have a nice set of heads.

I have never done this, but it is an old hot rodders trick and is still common practice today with old school engine builders. The claim is that it increases the port flow for those two exhaust ports, essentially making them more equal to the other 6 ports.