David,
I think the original Windsor decals were made on some sort of reflective vinyl material, so they may be hard to replicate. Disregarding the reflectance, I've had pretty good sucess replicating decals and printing them on ink jet vinyl paper. There's also inkjet decal paper available, but I like the vinyl stuff better because it's easily removable should you get the real thing. Once printed, the vinyl decals are fairly resistant to water and sunlight. I couldn't get a decent image with the Testors water slide decal paper and found it was well worth it to purchase the higher quality stuff being sold on Ebay or through vendors on the internet. The higher quality stuff just takes the ink better. It takes a little effort, but if you can find a decent photo of the decals, you can use the computer to rework them into a good image or create your own. Next to that, screen printing is the best though more expensive. However, an old sage (Dale) once reminded me that if you're out for authenticity, it's better to have no decals rather than an inaccurate ones.
Fred Durrette
Summerville, SC