Congrats on the new purchase - certainly, from the pictures Dave had floating around, the machine looks to be in excellent condition. Well done Dave  for supplying a great title for a really great price 

I know the boards are super rare - so you might have to invest in the board you pointed out. I THINK Centaur was in the production run after "Cheap Squeak" and before "Squalk and Talk".

My advice would be to check the manual on the game and ensure you are in fact chasing the right part - and - ensure you have the cables either in the machine, or with the board.

Sorry I can't be much more of a help, I have not worked on the Centaur II before... Let us know how you go !