I think these from this NBA Jam harness are the same ones used on the MK boards.
Weird looking...
Good idea about bob but I will wait it out for a bit.
the connectors in the last picture (with the JAMMA harness and the player 3/4 harnesses) are not what you're looking for.
the sound board interconnect wiring consists of the 6 wire power/audio harness and the ribbon cable. without one or both of these, you won't be able to have working sound.
you could always build the power harness, from .156 flat molex connectors and I think they're called trifurcon pins that you crimp yourself with needlenose pliers. I do it all the time, in fact I could just MAKE that harness if you really wanted.
the question however is whether you're running a Y-unit MK1 or a T-unit MK1. you could use a Y-unit harness on a T-unit board, as I've done it before myself, the only difference is the T-unit has a 7th pin for a 2nd ground wire, which isn't required, but if you're gonna make something for it, you might as well make it right.
I could alternatively sell you one of my extra Y-unit ones, and I'll just build one for a T-unit myself. I don't know what they're really worth, find that out and I'll make it happen for you.
I'm going to assume by your first post you already have a ribbon cable.