It seems there were several things used over the years to stop the heat under the carb, and the Rockwell manifold seems to be the most current (though not cheapest) option. Is there a general consensus on how well the Rockwell is working (sealing issues?, other issues?) now that it's been out for a while? Also, there was some talk about filling the crossover on the stock manifold with a product called HardBlock, but I don't know if that was ever tried with results posted. That did sound like a reasonable solution that may also allow a cracked manifold to be salvaged, but I've never heard any results.