Perfect. I figured that it wasn't necessary given the supply voltage for the LM1875 can be 16-60 VDC according to spec. I just scored some NOS LM379S amps from another source. Marco Specialties said they could not find them.
I replaced the dried electrolytic caps on the sound board, but the amp burned out before I could test with the game running. The game starts fine without the sound board connected, but before doing work to the board the game would not start, the credit display goes blank, a delay, then returns to attract mode. If the game was left to warm up for 5 minutes and a game was started then it worked just fine...
If it wasn't a dried capacitor that caused this issue I'm thinking it may be a failing Z-chip on either the sound or MPU board. Time to break out the logic probe. Thankfully my SC-01-A speech chip is still good. These are even HARDER to find than the LM379S.
The LM379S has a slight frequency "bump" around the 300-400hz range and another around 800hz range for speech according to my o-scope. So the amp will sound a bit more "honky" than the newer amp which is more natural flat EQ sounding. Most wont be able to tell the difference but some will if the speakers are original.