I've done probably 10+ intake gasket changes on different vortec 350's and the gasket has been the failure every time. The part of the intake that coolant came in contact with was slightly eroded in some cases, but no more so than what i've seen in a traditional smallblock with a steel head and intake running normal green coolant. The intake gaskets they used on these from the factory are ****. Felpro sells a redesigned intake gasket for these. Use those, and slightly coat the coolant ports on the head and intake with RTV before reassembly, and you won't have a problem again.