My guess would be a Venezuela-spec cab/chassis model with a home-made bed and cultural modifications.
Although the 40/45 tunnel shifter covers changed in 10/82 for the non-PTO models to allow for the raised space needed for optional 5-speeds, oddly Venezuela-spec trucks continued to come with the flat covers. A different floor panel did allow for a non-bench seat, although other markets still came with the split-seat version.
The 900-series serial numbers were used thru the 1980s for the Euro export models, but this particular number wasn't in that series.
Certain individual parts for the Venezuela-spec 40s and 45s were manufactured into 4/86 although the vehicle serial numbers were not published. So likely 900-series "VIN" numbers could have been stamped for them. However, I personally would want to see iron-clad proof that this specific truck was the very last one off the assembly line to believe the seller's inference.
The valve cover, air cleaner, cowl vent, tail-brake, lack of heater would be correct for the year and market.
The bed likely would not be authorized by Toyota--certainly not that tailgate attachment. Similar-looking but better-fitting beds were locally made in South Africa for their cab/chassis models.
South American vehicles are famous for hard-use and wet rust, so the respray job could be masking some nasty stuff. Purchasing sight-unseen is foolish, and caveat emptor--reputations are earned--good or bad.
At a decent price with a competent and very thorough inspection, could be interesting if all checks out. But likely will be sold on-line, expensively, to some unsuspecting enthusiast who will then blindly pass-on a provenance created and embellished to inflate a sale.