Gas tank under the frame and the filler below the bed says it's not a '51 either. That was a 47-48 feature. It seems to be a bit Frankensteinish. Maybe a big bolt cab swapped to a 1/2 ton frame. Floor shift would be a 4 speed or a 3-speed ('47 feature). Looks like it might have a 235 as well, from the 4-bolt valve cover and short pushrod cover.
It won't win any prized for originality, but looks like it might be a solid truck (from the pics, anyway.)
