Ther's an enamel called Kilz on the market for house painting. They sell it at Home Despot. I have no idea if it has any contraindications for an automotive application. It's a white flat brush-on (latex?) Might work. Sounds like what you're after.
I/I #4101
'71 GMC Jimmy 350, sm465, np205,3.73 posi.
'68 C/10 Stepside 292 (.030 over) Offy Intake, 500 CFM AFB,Clif headers, sm465, 3.73 posi.
'67 K/10 454 project.
'72 K/5 rolling frame project.
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