I remembered D talking about de Dion rear ends from alfa s but really a 1600 rear end wouldn't widen the rear track of a 1200 much at all.

So I wonder how hard it really would be?

All it is is a tube that connects the hub mounts and the diff centre mounting, could be solid mounted to car almost.

Don't need cool overs as the leaves still locate axle and work as springs.

This is what I've been thinking for ages!
Why not convert the axles off the IRS diff so you can mount leaves like a standard H-series diff?
Would only be a matter of cutting off the IRS crap, shortening the Diff and welding custom tabs for the leafs to sit under and bolt to.
Then you can figure out stuff like brake lines and handbrake cable routing etc etc.

Well looking long term at LSD but not a r31 cut down due to weight etc but see heaps of r180 and Subaru forester lsd diffs at affordable prices.

My query is could they be adapted to a cradle that bolts to the leaf springs?

This may be a dumb idea but better availability than r31 rear ends.

I wouldn't want irs rear end, happy with leaves just looking for LSD options.

Would possibly weigh same or slightly less than r31 rear too.