Ther gasket on the SM is just for exhaust. The water bypasses the face and goes around from the manifold to the tail like a Gil. But still, no liquid. You need the proper hi-temp gasket. You might make do for a weekend with hi-temp silicone, but that gasket is the least of your worries.

If you overheated the motor, there's a good chance you cracked a piston skirt. As the block gets hotter, the bores get smaller. You get reduced clearances and the pistons get squeezed. The slap noise sounds like rockers sometimes. It's really tough to cook synthetic- the motor is usually toast before the oil goes. I'd pull the rockers and look at them. If they're non-roller, your problem may be there. it doesn't take much to have one of the pivot balls overheat and gall- then crack.

Additives and magic cures are worthless. Damaged components are just that. Damaged. Be glad that whatever is wrong hasn't reduced your engines to worthless scrap. Yet. Running it and hoping is the fastest way to get there. If you have a cracked rocker and it breaks and sticks the valve open, the next thing is a valve thru a piston, then a broken rod and a windowed block. With any luck, the intake manifold will be salvageable. Same for a cracked skirt.