This info from previous thread - 

"A pass on note, posted here some time back by John, the Hoozier Hurricane. He noted that in some gasket sets, the rubber bolt rocker cover gaskets are apparently thicker than the original valley cover ones. He says that can result in some intake manfolds bottoming out on installation.. I trimmed the front one on my ECZ--B install, because it looked to be to close on clearance..."   

THREAD - http://forums.y-blocksforever.com/Topic147904.aspx

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Hey guys, be carful sinking those valley cover bolts in lower by using thinner grommets, I understand if those bolts are run in too far they may hit the cam below. I don't know how much you can go without hitting just be careful.