Beside all the fun that might come up here with that truck. Fact is, as said before: it is a Gas engine, else no foot starter.
Second: The steel quality for European understanding is not very high, so welding is not realy the problem, for useually the welding material is of higher quality (except sulfor and posphor content). (Truck frames by that time had at its best a quality of 22000 psi steel, which here is a simple construction steel with no further requirements.)
If the welding is taken of without or almost without any ´trace on the frame, it was so called cold welding, means the electric current was not high enough to burn / melt into the frame. Basically this weld is not existend (We call someting like that a glued weld.).
Third: The frames are could bend, the material is heat treated before the bending / pressing in shape. This enlarges with the propper material the strength of the steel, especially with the quality used.
Buy the way, Pick ups are of only a 14000 psi quality, which you can not buy in Europe. 22000 psi steel is something like ordinary construction steel over here, called ST37 or nowadays Q285.
Wolf