Just rebuilt and installed my motor, had everything apart on tables, parts and pieces everywhere. Somehow these got buried under the gasket kit box and forgotten. How important are they, and will running the engine "gently" without them cause any damage?

Thanks in advance!

That's actually a good question I've asked myself in the past.
I can't remember if they are meant to help stop cavitation and sloshing, or are meant to act more like baffles during cornering to make sure you don't starve the engine.

That being said, I imagine you could probably start the engine and drive gently at low RPM without too much of an issue with newer high quality oil.... but I'd definitely put them back in if you plan on doing anything else.

Basically if tis a SEMA build, you're fine haha.