Is the trans up shifted by electrical servos or by hydraulic like the old 727? If elec then why not just use micro switches to up shift and down shift( full manual ).
I saw a video of a guy with (probably a GM) transmission he set up like that. Had two (or three?) toggle switches on the dash. For every shift, he had to select the proper orientation up/down, down/down, etc. Every. Single. Shift. No thanks
That being said, it's probably feasible, just not practical.
If the controllers require the speed sensor and tone rings, I wonder how hard it would be to generate those from another sensor that's easier to mount
