Freeze plugs are installed in the engines when they are assembled, not at the vehicle assy plant...that's why there is no mention of them in the assy manual.
Don't poke too hard at it with a screwdriver, or anything sharp, trying to clean the funk out of it. If it is marginal, you'll wind up with another dadgum leak to fix!
Soak it down with your cleaner(s), and use a paint stick, or something similar to clean the doo-doo out of it.
Once you have everything as clean as you can get it, make sure you rinse ALL of the cleaners off really well. It doesn't take much leftover cleaning agent to ruin the paint, or make it not stick.
You do realize, don't you Jason, that you are climbing down into a hole you may never crawl back out of? The "while I'm here" disease can get you before ya know it! The rest(most) of us have been there, done that, and got the back-aches(and empty wallets) to prove it....
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Joel Adams
C3VR Lifetime Member #56
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"