I got my R42 line sign working! It lights up and scrolls through, the original lamps even still work! Thought you guys might want to see
I haven't wired up the proper plug yet, but I was able to find and order one so I'll do that next. Then, my plan is to make a nice display frame that the sign can sit in, as well as hold the power supply. I wanted to ensure I'm not modifying anything about the sign so it retains it's collector value.
For anyone interested, the power supply is here and the plug is here. I had to slightly increase the voltage of the power supply from 36V to 37.5V.