I have original Bally boards unless you are looking for new repro boards.

For Gottlieb System 1, I prefer the pascal MPU, and rebuilt power supply (although there are many aftermarket clones available--I couldn't say which one is "best"). I typically reuse the driver board, since often times it works fine. However, some people prefer just to replace the entire boardset with an all-in-one board (for a number of good reasons).

https://www.flippp.fr/boards.php

For classic bally, I prefer rebuilt originals or the aftermarket boards here: https://nvram.weebly.com/new-pcbs.html

I'm happy with all my pascal boards as well for my system 1's (and 80), really like the all in one board.