You're right about the dearth of search results. This one was interesting, notably the clutch and feedback wiring comments:
I'd start with having a full inventory of what model/part numbers are involved. That often helps find better search results. Then look at the wiring coming out of the existing equipment.
There's a fine line on the costs between retrofitting to old gear and outright replacement. Sometimes the time/labor/parts to engineer a retrofit meet (or exceed) the cost of new.