Don't, it'll look like doo-doo.....................
Stickers for most of the letters and black pen of the other will be ugly, if you go the pen route then pen them all.
When are you going to paint the strip on the bottom of the bumper?
Just order a complete set from Todd Jelle. Look under the Thunderbird Graphics tab for all the options. I had the reflective ones that were black in sunlight, but reflective silver at night.