Well, I finally got the 74AC240 I needed to build a bicore head. So I did. Of course once I finished it, I found plans for a more advanced version .
The light sensors are a pair of phototransistors with plastic lenses that I’ve been saving for just such a project. The motor assembly originally came with my tracked vehicle kit, which was replaced by the dual-motor gearbox. Really, what’s the point of a tracked vehicle that can’t maneuver? Anyway, the next step is to to mount the head on Rover, add some switches to signal the brain in which direction to turn, and, oh yes, install the brain.