Combines convert 1660 stick to 21 23 series

By stick I am assuming you mean hydro lever. I did that to my 1460. If the 1660 is wired like a 1460 and I think it is you will need multiple relays like the little bosch ones to isolate the 3rd solenoid engagement. If you have questions let me know.

How much did it cost you once all completedIJ Did you

I was also wanting to do that to my 1680 but wasn't sure if it was possible, to add the fore and aft, up and down reel and header, and unloading auger in_out. Kinda wondering if it's worth all the work or not. Keep me posted. thanx

I think it was worth it. I actually converted from the old style non electrohydraulic to this with the 21 series joystick all at the same time.