A better chance for 5.29's for the 9.5" diff is bolting a 5.29 9" ring gear to the 9.5" centre.
The two ring gears are exactly the same ID and OD the only difference is the mounting bolts (9.5" are thicker). The reason for the larger housing is to fit the bigger 9.5" bearing assemblies.
I know of a guy who bolted a 9.5" ring gear to a 9" centre with a little bit of work so a 9" 5.29 should fit onto a 9.5" centre with a bit of work.
This may solve the 5.29 rear for the 9.5" diff but the problem still remains for the 8" HP front - there is no option other than having a custom unit made at probably great expense or converting to the 8" Gen 1 LP diff.
Only front 5.29 options are 7.25" HP and 8" LP.
The odds of the Canter front live axle 5.29 fitting a IFS 8" HP assembly are slim to none.
I'm pretty sure the Canter front is low pinion anyway.