PS 3 steam kits us a PS 3/2 board is that what you're talking about, the wiring is the same as a PS 2 3volt board connectors! see item 25 below is that the board you're talking about?
MTH Electric Trains (mthpartsandsales.com)
50as10709i_Steam_PS3 Upgrade Kit Manual_2018 COLOR.cdr (mthtrains.com)
Alan