As an update and for future reference, I've done a pretty exhaustive comparison using posted original PTB stamping pictures. Using the two dimples on the firewall that is used to mount a circuit breaker for a power convertible top that were in so many pictures as a fixed reference and measuring that using a vernier caliper on my car, the stamp heights come out to approximately .80" so the ones that vendors like Eckler's sells as "exact" are in fact too large at 1" though the font looks to be very accurate. Even my original template I made in the 80’s from a tracing has a font size of approximately .80”. With the help via some CRG PM's and having fonts measured from a survivor
Z-28, those measured out to approximately 7/8" (.875"). So, I took an image of the Eckler's fonts, which seem to be accurate, and on the P gave it a slightly fatter bulge to match an original stamp, and had custom stamps made up by rubberstamps.com to have the size to be approximately .85".
Using orange model paint from Testor's and blending in some red to tone it down to match the hue in the many original pictures and using the Testor thinners to slightly thin it so it doesn't smudge up and with a dried single baby wipe as a stamp pad, stamped the fonts. With the Testor brand thinner you can stamp the firewall and wipe it off with a rag and not mar the surface if you want to redo it. This is with the firewall having been sprayed with a urethane paint. My friend was happy and so was I. Being it was my idea to have the stamps made up I kept them and attached a picture of my now stamped firewall and also included an Eckler's T stamp next to the .85" T to show the difference (the 1" was later removed of course
) For a not so perfect look I did a random hit with the stamps and however it came out is what I kept. The blotch on the B looks more authentic than perfect hits, IMO.
Mike