With EMs that have been sitting this long you really have to go through every stepper to make sure they’re all working smoothly and making good contact. Look for over fusing and hack jobs and take care of those issues. I don’t even plug them in until I’ve thoroughly gone through them. Clay’s guides are the best but Pin wiki’s em section is also strong.
And LEDs in EMs..well...might I suggest starting with good old 47s to keep the vintage look and feel? Personal preference, of course.