I've made a bit of progress in turning my recently acquired '8 ball action' back to its original Donkey Kong Juniorness. This involved tracking down some parts. Fortunately, the monitor bezel (surround) was installed backwards on the machine. All I had to do was unscrew the bolts holding it in and turn it around. (Easier said than done!) For the marquee, I had to go to Ebay. There were a lot of overpriced ones there, but after watching auctions off and on for a few weeks, I was able to find a decent one at a decent price.
I also had to remove the 8 Ball Action EPROMS/PROMS from the board and replace them with some DK Jr. ROMS. Fortunately, I was able to find a set at www.mikesarcade.com. The picture shows what they looked like pre install. I recommend getting a chip puller if you are going to be removing chips from printed circuit boards. You won't be as likely to damage your boards, your chips, or yourself. (This is the voice of experience--I once impaled my thumb with a chip way back.)
Here are some pics I snapped of the machine in its current state: