Stewart, the first truck I got was a 29. Like yours it had the dual high, flat disc wheels, worm drive rear axle, and a couple odd feature which were the supposedly early style head light lenses which I thought were unlikely to have ever been changed, and a GMI brand horn which I think was considered rare. Apparently they sold flat bed trucks with full length running boards and fenders the top of which were mounted to some sort of bracket under the flat bed. On mine the running boards extended a little behind the cab and had been whacked off at an angle probably with a cold chisel along with the splash aprons. The attachments for the fenders were under the bed as I recall. The second truck was a 1930 made before the body style change but having the 4 speed, bevel gear rear end, heavier front axle and Budd style duals. Most other features were the same as the 29 as I recall. I drove this unrestored truck a lot and it was just as you say pretty rough riding unless you loaded it. Sorry about the non railroad content.