That's dope! It almost seems like it had a 5th wheel before and it was used for towing.. a matching trailer perhaps? That would be even sweeter!
Late 70,s early 80,s saw a lot of Toyota 2WD cab and chassis’s being used for many different commercial applications. These came factory with the 3/4 ton rear axle (GO82). Duel rear wheels were not factory, but added by sellers to allow more weight carrying capacity. This may have started life as some type of 5th wheel application. Definitely was custom made. Attached is similar vehicle used as motorhome.