1969 COPO 427 ?

[PeteLeathersac]

Welcome aboard Mac!.
Have you perhaps transposed the last few #'s and the casting actually 3963512?.
If the deck stampings still slightly show, clean the pad w/ a solution (not sanding) so the stamping depressions themselves are truly cleaned out...using an old toothbrush may help..
When it's clean and dry, try a flash of white, yellow or other color paint that will stand out making sure the stamping depressions have become filled w/ the paint..
After drying, fine sand the pad surface only so the only paint remaining is down in the stampings then try again to see if they've become more readable?.
Sometimes shining a light at them on an angle seems to help read them too!.

Good luck!.
[img]<<GRAEMLIN_URL>>/beers.gif[/img]
~ Pete