I love our 1 tons because they're unique.
The 3800 is one cool AD !!
So's the 3804, frenz.
Hurthip, that is definitely not the original engine. I'm going to hazard a guess that it is a 235 full-pressure engine from the late 50's - a good swap - but a search of its number (stamped into a boss near the distributor) will tell all. The 3-bar on the cab might have been a local compliance measure by the owner who changed out the rear axle and put on the bed. That bed would not comply here, as it should be clamped to the frame and gasketed. Bolting to a horizontal flange is a no-no. But if the frame has no visible cracks - particularly where the front of that subframe is bolted to the frame - you will be okay to do it over, with gaskets and u-bolts.
The general condition of your find appears good. I'd get it if you like it. The swapped rear axle probably has a lower numeric gear ratio - for a higher sustainable road speed than the original truck, which was astonishingly slow and hard on fuel.
Even so, you will be paying more to make this heavy old horse work than you would for a half-tonner. So she won't be the best daily driver. But that, right there, would be a real truck, not like these little bitty imitation trucks you mostly see...