Actually, the 3B and the 13B-T were regarded as the best diesels fo their time. The 2H wasn't as durable. 3Bs can run for 600,000km with NO SERVICE except oil and filter change... I know because the Old Faithful still runs and is not an oil guzzler. Never had anything done to the engine, apart from replacing the glow plugs twice...
You havent heard of the aussie HJ60 with 1.3 million klms yet?? Toyota Australia used him and his 60 in newspaper ads.Its only had a clutch and alternator replacement.
I think a 12HT would run rings(excuse the pun) around the B engines for longevity. NeaRly all the aussie HJ61 have post 400000klms on the clock and going strong