Ok, because I like testing stuff, I know the temperature of the top of the inlet manifold during normal running. It's about 70°C fair to say the underside is a tad bit warmer.
Also, you're talking about alloy head and manifold.
My point is that this is a surprisingly harsh environment. Would those bolts work? Maybe. Is it a good idea? Not really.
As ever, just my opinion, tis your car to do with as you wish