The Mazda 2.2L NA was used in the Rangers between '83 and '84, and for '85 and onwards (till they stopped importing them), they used the higher power 2.3L Mitzi turbo engine. It was also used in the '83 and onward Mitsubishi mighty max and Dodge D50 pickups (mine has the dodge tags on it). Seems to be a good torquey engine, especially when the turbo kicks in. And yes, they are very rare in the US. The emissions place here had never seen a Mitzi diesel before, and kept marking it down as an Isuzu. I've seen a few for sale recently in CA and WA, one of which had a spare engine that came with it... wish I had gotten that one. The Northwest seems to be the best place to find them, but unfortunately I haven't located anywhere good to get parts from yet.
Are you laying down black smoke with biodiesel? Mine couldn't pass emissions on dino-diesel, but I switched to bio, and reset the fuel screw and timing, and smoke dropped to 18% of the limit (7% opacity). The emissions guys were amazed. Interestingly, the timing tools for the VW fit the injection pump fit this pump perfectly -- could it maybe be a bosch, or interchangeable?