Steel shim gaskets leak? Not if the heads and block are flat. AFAIK exactly NO B or RB engine came out of the factory with anything but steel shim gaskets. The same with all V8s until maybe the early to mid 80s, when I believe the LA started using composition gaskets, which prompted the reduction in block deck height from 9.600" to 9.577". Shoot, the intake gaskets on my Poly motor were steel shim! As were the exhaust pipe gaskets.

Look in the factory service manual and see if they recommend spraying or brushing any goop on those steel shims. I bet they don't. If they do, copy the page and post it because I want to see it.

To my way of thinking, adding Copper Coat or Hi-Tack or aluminum paint before installing the gasket puts two slippery layers between the gasket and the block or head. The gasket is coated with what the gasket manufacturer wanted to be there.

Back in the day, when Chrysler was forever quitting big block engines, they sold 452 heads for insane prices, like $45 each. The 452 head, like all big block heads since the 346, has an intake port that is easier to work especially when installing larger valves. So people started reworking them. They also had hardened exhaust seat areas and some thought the entire chamber was hardened.
Anyway, the most magical thing about the 452 heads was the fact that they were available brand new by the pallet load for insanely low prices.

If you are looking for a 452 head to port, keep your eyes open for the heads with the numeral "!" cast into the end of the head. These heads were a revision and would have had their own casting number except that Chrysler had already made the decision to quit making big blocks. So the heads got thicker ports and maybe slightly better contours.

R.