Years ago when I ran big blocks I never ran any gaskets with the valley pan, just a dab of silicone in the corners of the china walls. I reused them multiple times and never had issues.

That will work when EVERYTHING lines up just right. As soon as you cut something or throw in some aftermarket parts, gaskets can mean the difference between success and failure.

Yes sir, Nothing was really changed just r&r for cam lobe inspection, gasket replacements and paint/detail work. The heads were not removed and all same parts reinstalled.
Copper

Years ago I ran a 440 w/ some severely shaved 915 heads on it. Shaved enough that I had to notch the corners of the intake manifold to clear the china rails on the block.
When I tightened down the intake, it crushed the valley pan down at the corners, but port alignment was still correct.
I didn't use any gaskets on that one...ran it for years w/ no problems.