If you mount the rear tractor on a fifth-wheel setup on the drawbar of the front tractor, all you need to do is adapt the clutch of whichever tractor you are not going to drive. A hydraulic clutch setup you can latch in place enables you to release the clutch on the dummy tractor from the driven tractor. A hand M&W clutch is easy to adapt to remote operation also.
Then you can dismount, shift the dummy into gear, set the throttle, and return to the driven tractor to engage the clutch.
You need a remote kill switch for the dummy tractor.
If you are driving the front tractor, the steering on the front will steer the entire outfit. If you are driving the rear tractor, you need an extended steering shaft from the front to the rear with u-joint over the fifth wheel. Easier is to put independent power steering on the front tractor and run hoses to the rear tractor's steering wheel/control valve.
If you drive the front tractor you need oil pressure and temperature remote to monitor the rear engine. For rear driving, you can see the front tractor's gauges and exhaust well enough to stay out of trouble.
Since Farmall's run wide open without load with no problems, there is no reason to try to set up remote throttle control. If you need less power, throttle down the driven tractor, until you remove the remote tractor entirely by using the clutch.
For serious work, independant dummy brake controls are nice but not necessary.