A possible fix which may save you a world of aggravation. I had the same issue with the hood on my TR4A: no sign of holes drilled for the lettering. I mirrored the pattern which is on the trunk lid, and drilled the holes but it was a nightmare. Despite having a good template, a minute variance when drilling will result in crooked letters and a potential source of rust down the road.
What I did was adopted current technology and 3M tape. By taking a set of letters and cutting off the mounting pins you end up with a flat set of letters. I found that a wire cutter and a Dremel Tool worked well. Then it is simply a matter of applying the 3M two sided tape to the letters, trimming the tape with an Exacto knife and applying. I took photos of several cars at a recent Triumphest and figured out the spacing and positioning from there. The advantage of the tape method is it allows you to temporarily position the letters and adjust as needed. This is something you cannot do once you commit to drilling holes in your hood or front apron.
They are as secure as any lettering on any current vehicle as that is how all manufacturers current affix most trim.