Yep, that model was a rebranded Isuzu Pup. I had an 81 that I inherited from my brother. He got it in 86 or so for $600 (with 100,000ish miles) when he got out of the Army. He drove the piss out of it for 2-3 years and put about 50k on it, but he never changed the oil!! When I got it around 145,000 ish, I changed all the fluids, and I remember the oil was like molasses. I ran some kind of cleaner, maybe some diesel or something in the crank case and change the oil after 10 or 15 miles. I had that truck for 70or 80 k . At this time it was over 220k and did not use a drop of oil! Just incredible considering the abuse my brother put it thru. My dad took it when I got my first sports car, and he put another 50 or so on it. Un fortunately he hit something and the radiator sprung a leak. The enging got so hot that the plastic fan blades deformed and cut into the radiator more. At this point we scraped it, loaded it up with scrape and drove it the 20 miles to the scrape yard. I am surpirsed that it made it, and did not blow up on the way there.
I firmly believe that isuzu motor was one of the toughest ever made! It was not a fast truck by any standard, and almost so slow on the highway to be dangerous, but man it was bullet proof when many motors where getting rebuilit at 80-100,000 miles.
Brings back memories! Dave