Just did the swap from Centaur II to a Centaur cab. You need to create a wiring harness for the lamp insert board/displays or modify an existing harness. Its time consuming but not overly difficult - all of the info is in the schematic to match the wire colors to an existing harness or build your own.

Not if you were swapping from a Centaur II style cab to a standard Bally Cab it wasn't. The display harness for example is way too short to be used on a standard insert panel. Not to mention the splitting of the controlled lamps on a CII cabinet between the mini backglass and the display panel. Depending on how you mount the boards in the classic bally head the rest of the harness can be made to work but a couple things need to be extended to have a clean install.