Thanks, guys!
I tried some lacquer thinner and some acetone last night with no luck. On another forum, I saw where a guy was basically floating a fine flat file over the deck surface that he was wetting with WD-40, and this seems to be doing the trick. Cleaning up the rust/corrosion around the water passages, too - not removing any real metal, but leaving a nice bright surface now.

And good info on the gasket thickness for the 400/440 - that should bump my compression up from 7.98 to 8.01:1!

Thanks again,

Clair