1990 360 engine, trying to retrofit it to use a mechanical fuel pump.

Don't clean it. They have a coating, can't remember what, that makes it look nasty, but it needs to be thete to help prevent friction wear.
are you thinking of the moly coated ones?

https://www.manciniracing.com/moapenec.html
i've never seen one in a stock motor. always just the usual stamped steel jobbers.