tempforce:
Mazda had that 2.2L N/A Perkins diesel in their US pickups in '83-'84. Longbed in '83, short in '84. All of them had a 5spd trans, but the gears were not all the same as the gas trucks. Rear gears were lower, maybe 4.11 or 4.56?
My '83 got 34 MPG in mixed commuter driving.
Best was 42 MPG cruising from Sunnyvale to Willow Springs Raceway @~60mph, just me and one Open Twins racebike. At this pace, I could do the entire trip on one tank of fuel, about 720 miles, IIRC. Mostly on I-5.
Worst mileage was 28 MPG, to the same destination, but run @80-85mph. (85 was max, it sounded like a sewing machine on steroids. 80 was more comfortable sounding) This was with two of us with two bikes, one on a little bitty trailer. Couple times going downhill, it was faster in neutral.
We got a really late start, so I was pushing hard.
Most of the 2.2 Rangers only had a 4spd, and they weighed more than the Mazda, so fuel mileage was not as good. I don't think I got more than 28-30mpg in the couple Rangers I had.
Ford really screwed up by using the Mitsubishi Turbo diesel. That was a very light duty engine, and a bit delicate. They would have been a lot better off if they had put a turbo on the Perkins engine. That is a true industrial engine. I had a diesel big rig repair shop take one apart, and they were impressed. They expected it to go 250k before needing a valve job, and 500k before a rebuild. Said it was built exactly like a big rig engine, with press-in cylinder liners, and other details.