Chevrolet ran off a relatively small batch of the basic vans, maybe 4000 or so, 3,658 of which went to a sub-contractor to be converted to K51's. Hence the unconverted basic panel van is now rarer than the rare K 51. Erik Jostad has / had the nice basic van pictured.
All the K 51s came with a generator in a Ben Hur one ton two wheel trailer. All those generator trailers had a 7.50 x 20 spare slung under the back, because there was no room for one in the truck, thus the trailer carried the one spare wheel for the whole combination.
Some of the original van spare wheel mounts were torched off during the conversion and the cut ends are still on the K 51's, others were completely removed ( even the stub would be a big lump of metal to waste ) You can see from the van picture that the original spare was slung just where one of the large side boxes went.