I did the exact same thing to my 1650. You will need the double spool valve, the lines that run to the front, the female couplers and fittings,the second spool control lever, don't forget the connection links. You will also need the lines that run from the hydro to the spool valve. If you want it to look factory you wil need all these items. I was able to get them on epay. I have seen at a plow day a guy went with a green spool and routed one on each side. I also have a connection where I can get the male couplers that fit the factory female couplers if you or anybody would be interested at a fair price.
