i just changed from wet bassett twisty headers to wet logs on my 460 and had the same problem..
do you have a ford?
i know of 1 problem is most of the gaskets are for regular 460 heads if you have cobra jet heads the ports are diffrent on the gaskets but not the logs and it will blow the gaskets.
if you use high temp silicon instead of a gasket it works great!
or if you wanna run over transom twisty headers and have a ford i have a set for sale including all the water injection lines?
try the silicon i know it sounds diffrent but works great! i have not had a bit of problem yet... i did the same on my last boat and never had a problem