all the mazda boys are using hilux diffs
i'm putting one in my CA coupe
8" ring gear, heaps of ratios, big fat axles ( 30 spline vs bw 28 spline )

R200 is an irs centre ( no axle tubes ) come in silvia/skyline etc.

what are you doing about brakes and stud pattern with the hilux diff?

My advice would be the 8" hilux diff. If ya look in the SUMMIT catalogue, there is a complete centre section available for it made by Detroit Locker & another by Powertrax, bound to be able to handle abuse!
You can shorten it too if you wish and i've seen many with modded bolt patterns. My next project WILL have this in it.

1200's use leaf spring rear suspension just like mopars. You could "copy and scale down" the staggared leaf spring set up used on all high tq/hp. There's lots of photos of cuda's etc with front wheels off the ground and STOCK rear suspension with slicks.
Right rear leaf stack has same number of leafs as left side, but right has longer leafs reaching forward, and has the shortest one or 2 leaves reaching fwd of axle u-bolts, but not extending rear of axle (acts as a ladder bar).
Left side leaves are standard, though some had 1 or 2 short leaves extending rearward (opposite direction of right side). Let me know if your interested, I can send photos and measurements of each leaf.

i'm changing the front to ford xf discs. same pattern as hilux.
you can redrill to 4 stud as hilux is 5 on 4 1/2" datto is 4 on 4 1/2" so you only need to redrill 3 holes