Yes, the etch "metal ready" or new name "prep and ready" is made to prep surface before coatings are applied, but the POR-15 was originally made to react with rusty metal, and I never had luck with it sticking to "good" metal. I did the same thing you did 10 years ago
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1970 T1 W/MassIVe 2913cc RAT/?EFI? w/direct fire (very soon) and 915 trans
1962 SC 1776cc SP 944NA brakes, 993 wheels
VKG