The BUA61 was the somewhat shorter early version? My Japanese isn't good enough to quite tell...
That was the original project code and the first chassis built from August 1961 through to march 1963. But in true Mazda style there were two versions of the BUA chassis and the BUB chassis even though there's no mention of it!
It was the basically the same dimensions as the my BUB61. The main external difference were(on most models!) was the grille, side front indicator lenses, side chrome moulds and guard mirrors. But again even for the very small amount that found their way here, we got different versions to the JDM models.
The BUA61 has the 9 slot grille and the BUB61 had 13 slots. Most BUB61 got the side chrome trims that ran from mid guard and along the door. You could get this though on the earlier ones as an option - you could say you could factory pimp your B1500! Most early versions only had a drivers mirror where the later ones got both, although I haven't seen too many JDM brochures with both fitted.
But as most of the brochures say as you have probably read, its the utility vehicle for the highway era! Trust me, it's very scary to drive at any speed, let alone highway speed!