Mike, keep in mind that the heater/AC box must also be swapped along with the late dash, since the defrosters and cabin heater outlets and their hose sizes were also changed. Getting the early bowden-cable controls hooked up so they work right might also need the late 3-lever controller. It's been done but not simply nor cheaply.
I've read conflicting reports about swapping out the heater/AC box. Pantera Doug has done the conversion by simply modifying the existing box.