which gasket goo?

if you have machined surfaces for water pump, and a paper gasket, smear some loctite 515 on the gasket. 300deg stuff should be alright to do exhaust manifold, but i generally like to use dry gaskets for intake manifolds.

Only really need sealant around water jacket hole on inlet manifold. Aviation #3 fine for that & water pump.
Been told by mechanic that different temp silicones is only of concern if running engine immediately - once cured all withstand same temp!!

Cheers, Gregg