parts from a '97?!?!?!

[Longhorn Man]

I work in a diesel and fleet shop. I've seen quite a few Vortec 350s with 600k on them. Had one the guy had hoped to get a million miles out of, but it blew at 750ooo.
There's a lot of things that will shorten the life, overheating/blowing head gaskets is one of them, the main thing I've seen that shortens the life is if the intake gaskets leak into the engine and goes without notice. It's more common than you'd think. Not saying it's a real common issue, but it is somewhat common.