Sealing headers
My buddy and I double gasketed his and used locking bolts to keep them from backing out. The hookers on his 383 are terrible and we've fought them the whole way. We used Mr. Gasket gaskets, glued together with ultra copper, and these:
http://www.summitracing.com/parts/STG-8932/?rtype=10
So far so good. Hope this helps.