While there's about 4 inches difference between the 727 and 518 2WD, I cannot say on the 4WD, but I'd bet they're close.
The controller needs at least a speed sensor to comply with the speed presets for OD and lockup. Been in contact with Gear Vendors, and their controller goes for $100. Now I need to find out if it works with the Mopar 4-speed auto.
The 99 cent toggle switch method only requires that you remember to use it when you want.
I just received a new overdrive section via eBay. Some readers here know of my snail's pace mods I'm doing. Anyway, the engine essentially had a free 46RE with it. Thus began my education. A 46RE is lost in an '89, so I'm backwards engineering it to become a 518. Basically that amounts to taking all the electronics out and putting the pre-RE stuff in. Initially, I was gonna swap out the output shaft and governor assembly from my A500 to the improved 46RE, but using the A500 OD case for the speedo gear drive. Last week I saw the OD on eBay. $175 plus shipping put it at $201. Now, to me, that's a bargain, since I was gonna have to pay someone to break the OD down with a hydraulic press, or buy my own press. Now I can bypass that process and just bolt it on. He has more in 518-46RH, as well as 46RE to anyone interested.