You are lucky. Making dark number decals is the easiest type of inkjet decal to make. White and light colored numbers are a real pain in the butt. Finding the right font might sometimes be a problem, but in your case you should be able to photograph the numbers. Shoot them from straight on, then import into a photo editing program. Crop to just the number, and resize to fit. The remaining problem in your case will be to match the decal color to the paint. You may need to mix paint to get the shade you want.
I'd try to mix up some paint, paint a sample, scan it or photograph the sample, then use your graphics program to sample that color and use it for the color of your decals.
I use the decal paper sold by Micro Mark.
Oh, remaining problem is overcoating decals without dissolving them. They need to be overcoated with a clear, because most inkjet inks are not waterproof. They are not proof against clear paints either! I use Testors glosscoat or dullcoat. I mist on the first coat VERY lightly. When that is dry I put on a second light coat. When that dries I can generally get a good final coat on without dissolving anything.
Because of the problems with making inkjet decals, I always duplicate the final artwork three or four times so I have a lot of samples to work with and make mistakes. I print them out together, cut them apart, and use as many as I need to get the job done.