Looks like a typical farm truck that someone modified. The only thing stock on the instrument panel is the two large round gauges. Everything else has been added. Looks like they did a decent job of putting in the Pontiac motor. They probably used a 55-59 GMC clutch housing to make it work. In your first post you asked about changing the hoist. It is a grain truck, not a dump truck to haul dirt with. It was built to where the tail almost hit the pit and the dump angle for grain does not need to be near as steep as for dirt. If you want to haul dirt, you need to get a dump bed instead of a grain bed or just whack off the back of the bed even with the frame. Looks like a lot of improvising from installing a V8 to switching to 12 volt to using barrels for saddle tanks, adding a tach, using a radio out of another vehicle. The PTO and grain box could have been dealer installed.
