Gorgar does show up from time to time with the 6A board, and it's fine to use that board for any system 6 game. Converting between the 3 and 6 chip layout is just a single jumper, and a number of 3 chip games came with that board from the factory.
With the driver board there are minor differences as the design matured, but as long as it has the big red pill resistors in the lamp circuit (or had ceramics swapped in) it should be fine. If you see 0-ohm resistors in the switch circuit (only a single black band on them) then it was intended for System 7, but it will work. Supposedly you may see some phantom switch hits if you use a system 7 driver in a system 6, but I've never seen it personally. A lot of people use the rottendog boards, and Kohout is very nice too.
For the sound board, any of the williams pinball system 6-7 sound boards with the speech connector will work. If it didn't originally use a speech board, it's just a matter of removing one jumper to convert it to take the speech board. A number of vids also used the same sound board, and they would work, but with a lot more jumper changes. Kohout (pinballpcb.com) has new production speech/sound boards if you can't track down a good working set. Very fair price for them I think.
When it comes to power supplies, avoid the rottendog for Williams. They have a lot of issues with the high voltage regulators. The factory boards are cheap and easy to get, and easy to fix if needed. Pinscore / X-pin boards are very nice, I'm using a pinscore in my own Black Knight. Kohout also makes a power supply and I like the looks of it, but haven't used one myself.
Right now I'm temporarily shut down in the repair work, in the process of moving cross country and still staying in a temporary location without access to all my stuff. I do appreciate the recommendation though
