318-3 Closed Chamber Truck Heads

70coupe said
So I guess my real question, does anyone see it as a problem to run water through an Edelbrock performer (Non-EGR) crossover instead of exhaust. Assuming I seal the gasket nicely I don't feel it will cause any issues?.

I don't know. I would use good composition gaskets and SEAL them around there.

So far as hardened seats I would not bet on that. Those heads were MEANT for hard, heavy pulling and to withstand HEAT. That was their purpose