Maybe ring Chris at Povey Motors? FYI you’ll want to find a diff out of a car that has the same speedometer gear ratio as they changed to a finer-tooth tone ring in the diff around 92. Yours SHOULD be the earlier style (speedometer would say something like r 6298, which is sender pulses per km; later cars have something like r 24059) so you should be able to source a diff from an 86-91 240...just be aware there are several diff ratios too, although 3.73:1 is most common on the later autos...M47 5-speed manuals may have a lower number diff ratio (lower revs).
