If the UV map is too awkward to add the numbers direct to the skin itself, then the next best option would be to make the numbers a separate mapped entity, similar to how Kunos handles the liveries for their modern F1 car DLCs like the F2004. @SATLAB90 made his Jordan EJ11 mod using this same technique for the sponsors on that car, so if you want to learn how to do it, he's my first recommendation.
I did try shrink-wrapping a plane to the body for the FIAT (which had similar UV issues) but it needed so many tris in the plane for it to look good that I decided not to use it and just take the hit to accuracy by moving the numbers elsewhere. One of those compromises that comes from wanting to keep the tri-count down for better performance versus wanting to be as accurate as possible.
If there's a way to do it with that doesn't take thousands of tris then I'll definitely use it.