If it has an ove3rdrive, it will have a fourth extra lever (main, red hi/lo, yellow hi4) sticking out of the transmission hump about four inches forward of the seat box, on the RH side. It is quite possible that it has been removed, as they were not the most durable gadget made. In this case there should be a hole there, possibly with a cover, although replacing the panel would not have been hard.
John

