Thinking back, I'm reasonably sure I MIGHT have hit O/D, but I KNOW I didn't L/U.
In stock form, The O/D, though engaged via a solenoid, is still a hydraulic function. The solenoid opens a valve that sends fluid to the O/D piston. In this valve body, he just directs fluid physically just like 1-2-3.
The L/U does remain solenoid activated, and I haven't yet gotten that circuit completely wired. Initially, I will switch it on/off nice and simple. Eventually I figure on something where IF I'm in O/D, AND vacuum is up, L/U will engage, but IF I hit the brakes OR vacuum drops, it disengages.