There's no problem going with incandescents. I personally prefer the warmer light of the incandescent bulbs.
I would recommend using #47 bulbs since they put off less heat than #44 bulbs. I personally am not a fan of LEDs in older games (generally), and as long as the game isn't going on route there really shouldn't be anything to worry about there. Only thing i would do is make sure your general illumination connectors are good...replace pins etc as necessary for long term reliability.
Get the cleaning stick and the sockets. Bally's from that era are well known for crappy lamp sockets so get plenty of them. Still might be able to use the cleaning stick anyway, so for a few bucks extra why not.
Good luck, Mystic is a cool game!