We have a 7120 with auto steer I would like to move it to our MX 285 or 270 but I am not sure how to tell if the Tractors are setup for the auto steer and if so where are some instructions on how to take it from the combine to the tractor
CIH does not support NavII AccuGuide on MX270 or MX285 models, only on the Magnums (245, 275, 305, etc.) You could put Trimble Autopilot systems on, and reuse your receiver and NavII, but you would need a new display and some additional componentry on the tractors, and you would have to have the NavII reflashed to run Trimble software instead of CNH software. Then when you're ready to put it back on the 7120, you'll need to have it reflashed.
Reflashing is not something your dealer can do; the NavII must be sent to a Trimble service center, and it will cost around $75US each time (plus shipping and insurance).
The top of the front axle king pin will have wiring coming out, along with wiring to plug the nav 2 in behind the panel behind the seat. Along with the pro 600 you need the nav 2. The nav 2 is on the floor to the right of the seat in the 7120, it goes behind the seat in my 275 no sure about the 285.