[DaveW]

Hi Wombat,
I used to work for AMI / Toyota (20 years), not in the 60's or 70's but i know heaps about the the MS series crowns from that era,

The rear axle assembly is almost identicle to the EJ, EH, HD, HR, holdens, only about 5 mm difference in the track.
The axles are slightly longer, Toyota PCD and were made to suit imported brake setup initially which then changed later (early 70's) to PBR.
I believe a Holden rear assembly will bolt straight in. Rod hadfield or Hoppers Stoppers have disc brake conversion kits for converting the Holden version.
The diffs have ratios available 2.78, 3.08, 3.36, 3.55. 3.89:1 there was also LSD available in some models up to LX Torana. the spider gears are the weak link in these diffs.
Also, a guy in Traralgon Vic has a Crown Chassis Cob with an LJ complete rear axle in it.
The track is about 100mm less, which is great for the dished wheel look,
I dont know his contacts though.

Dave