Welcome to YT.
I would suggest investing in the service and operator's manuals. OEM is the best to start with I believe and there are a number of them available on eBay as one source. I don't see a 455D service manual listed in the store of this site.The service manual for the 455D appears to have 11 sections to it, so be sure any manual you look at is complete. Section 3 is electrical which I would expect to have the info you need to rewire it in areas if needed. Messick Farm Equipment is a place to check. (https://www.messicks.com/nh/67088
) Check out the electrical sections of the catalog. They show the harnesses, not in stock but as available in a few days. A phone call could confirm if that is correct. There are vendors that make replacement harnesses, Brillman is one and there are more and someone may add more names for you to check out.
An operator's manual should give you information on all the control functions.