Not sure what the go is with the file you posted Gav, but the 71B boxes I have in the shed (240K, "skyline ??", L20B bluebird and Z18 bluebird) all have a bellhousing flange around 40mm thick, the bolt your parts manual shows is only 30mm long so wouldn't even get through the bellhousing to engage in the block ?
The original 4 speed from a 1600 has a thinner flange, not sure if a 71A box may also be thinner ??
Anyway, easiest way to be sure would be to measure the thickness of the bellhousing flange on your gearbox, measure the depth of the bolt holes in the block, add the two and get a bolt a bit shorter than that measurement.
Also bolts "27" and "28" are labelled "Bolt - fixing T/M to engine", are much longer (and some are thicker), yet are shown in the pic as joining the rear ext housing to the front ?
Got to go out for a while, I'll find a bolt in my spares pile and physically measure it.
Edited by 1600dave, 10 June 2017 - 09:42 AM.