Can I suggest that the numbers can be enhanced. First clean the area around the area and numbers.
Choose a thin paint in a colour that contrasts the background/substrate, perhaps yellow, silver, light blue, white. Dab the paint over the area filling the number stamping, and immediately wipe over the number stamping removing all excess paint but leaving the number stamp filled with the contrast colour. Hopefully the numerals will show more clearly.
I am going to try paint stripper and a brass wire brush to fully remove all traces of paint from within the numbers with the aim of getting them to be as visible as possible in the hope that I can then just mask them off during painting and simply clear coat the numbers after.
If they still do not show well I may try the colour contrast idea (like black) to make them stand out more, but this may give the impression they have been tampered.
I have photos before and after but anything that looks wrong will always be an issue.