I believe the Toyota trucks are very well built, but I can't say if they are easy to work on. The Japanese had a very good design approach in their vehicles, it appears that vehicles designed for the Japanese market were built with fairly standardized parts, brake master cylinders may swap between different vehicles, it seems there was high level cooperation and design effort between various manufacturers.
The 1986 -1992 series of Mazda trucks were built for the Japanese market, later export. Parts from all those years are fully interchangeable. I can take the entire truck apart with 10, 12, 14, and 17mm wrenches and sockets, apart from some driveshaft and transmission work. The rims are 6 bolt, which I believe makes the wheel mounting particularly robust. The original engines were prone to fail due to the overhead cam running in milled aluminum races rather than proper bearing shells. Any coolant contamination in the oil would damage the head. They can be line bored for bearing shells.
However, the previous series 2 liter Mitsubishi engines fit with custom motor mounts. Those are found in Ford courier trucks from 1972 onwards, plus earlier Mazdas, and very similar to the industrial 2 liter in Mitsubishi forklifts from the 70's and 80's. The manual transmissions have interchangeable parts, bell housings and tail pieces interchange, allowing for a very nice swap. Intake and exhaust are on opposite sides in the different series.
The cabs were made with galvanized steel making them quite durable. The boxes tend to rust out. When running well I would get 35 - 38mpg. The rear suspension was weak, adding 2 spring leafs per pack improved handling and load capability.
I would like to find a more up to date engine swap, preferably fuel injected. I suspect the 2 liter Chevy Cavalier engine may be related. 2.3 liter 1996+ Ford Ranger, 1998+ Kia Sportage, Ford Probe all appear to be compatible recommended swaps. There's ample room in the engine compartment, even a 4.3 or 350 will fit. Which is another thing I really like about those trucks, easy access to all systems and components. Fender mounted 1 gallon washer fluid reservoir, allowing easy changing of summer and winter washer fluid with a siphon. The fuel tank is mounted on brackets and can be dropped without having to remove the truck box.