Quoted from damadczar:I don't wanna take my back glass off to double check, but I think you'd need:
MPU
Driver
Power Supply
Sound
Speech
I'm pretty sure they sell a combo MPU + Driver board, and I think there's also a combo Sound + Speech board (I think).
I've not done an exhaustive search, but that's mainly what you'd need.
Is the display driver board also missing? If so, you'd need that too.
I would second getting a set of teh Wolfpack displays. The kit has the master display and the 4 slave displays.
For the others you have a few options. Get original boards for the game. Those when properly serviced and rebuilt run well and are trouble free. I run all original boards in my Blackout and Firepower and they have been solid for years.
For the MPU/Driver if you want an aftermarket the latest version of the Rottendog Combo board works well. The early version wasn't as robust in regards to the switch matrix and if there were shorts in the matrix could blow an odd chip in that board. It also had a mounting tab you needed to watch out for. The current version doesn't have those issues. I know several people running them and are very happy with them. So either a combo board like this or a rebuilt original MPU and rebuilt driver board.
For the Power Supply I prefer the original one. They are really simple. As long as the main 5V capacitor is replaced and any questionable solder joints reflowed you are usually good to go. I rarely have issues with the HV section for the displays but if you run the Wolfpack LED displays it isn't an issue as those don't need HV at all.
I've heard there was an aftermarket sound/speech but never tried one of know if they are available. Again, I go original here. It uses the smaller square sounf board with the optional 40-pin ribbon connector. That is needed so the optional plug in speech board can be used. It holds up to 4 speech ROM's and some circuitry for the speech. Either find a good used one or a used set that can be rebuilt.