Thanks John (@j-healy), Spiros (@fiveten), and John (@johnb).
I had read the forum entry (I think it was Brit Modeler, but not sure) where Kursad of Caracal Decals had mentioned that the FJ-4 decals were in work. That thread is several years old now, so I am not sure what the status is. I suspect that at least part of the delay can be attributed to difficulty in finding good photos, but that's just a guess.
I had elected to go the painted markings route early on. Even if I was able to locate the Matchbox decals, I would have probably scanned them to make the masks. This is all part of my desire to expand my skills. And speaking of that, I have been struggling with those very same masks since two days ago. There's a variety of reasons.
First, I work with the software so infrequently, that each time I use it, I have to basically start over. I am trying to rectify that by taking better notes this time and being more organized about the artwork.
Secondly, I spent a bunch of time on the tail letters ("NJ") , specifically, trying to reproduce the opposite side from the drawing. Silhouette Studio has only basic graphics tools and it took a lot of trial and error before I managed to repro that second side well enough.
Thirdly, despite my best efforts, every time I tried to import scaled VG files into the Studio software, it would give me trouble and also come in too small, requiring me to resize the image afterwards. Frankly, I think the software is pretty flaky.
The upside is that my file organization is better now and once I get more of the artwork done, I should have at least some art that can be used elsewhere (national insignia, lettering). And I am making sure to take better notes on things I encounter and problems I solve so that I can refer to them next time.
The guidance transmitter is still in the same condition since I have done no actual plastic modeling since early yesterday. Tomorrow, I have to finish a restoration of a clothes dresser for my wife for Mother's Day and I have scheduled some time to work on my cabin cruiser.