Having a critical eye when looking at ads that are posted by people with no real idea what they have is the key to separating the wheat from the chaff.
Price is way to high. This is a parts truck. $1500 TOPS and even that would depend on the engine bay condition, cab condition, brakes and how bad the frame is mangled by that bed.
Most sellers don't realize that buyers have the HUGE extra cost of hauling the truck home. So even IF this truck was 'original' (had the bed, spare tire carrier, fuel tank and all the other 'generally missing' parts) you have to tack on $1000-3000 to haul it. I've had to pass on many parts trucks that were more or less 'complete' simply becuase of shipping. There might be $1500 worth of parts, but there DEFINITELY NOT $4500 ($3000 hauling fee) in value.
That is the single largest detriment to selling large MVs that don't run. Your potential buyers base is local, unless you have a very rare truck (this is not one) or are selling at a very good price.
And as for the 3rd axle.... if you look, the splash guards clearly show the only rear axle. There is no way to mount a splash guard between the middle and rear axle.
This is a bubba'd up G506 Chevy that was most likely a farm vehicle (hay or some such) and most likely severely overloaded (1.5 tons is not much on a farm) so you would most likely have to check the frame and the axles much, much closer.