Congrats on the Shadow! You've been looking for those two for a while I believe.
Here is a thread on some thoughts on putting a 5V display in a Bally/Williams machine. A couple of options discussed are using a separate 5V power supply or tapping into the 12V on the Williams and then stepping it down to 5V.
https://pinside.com/pinball/forum/topic/stern-red-5v-led-dmd-in-a-williams