All I've ever seen/heard of on Connects is people attaching, as your looking at doing, FRS knuckles to the rear axle. That's just a solid tube mounted on leaf springs, very 60's.

Whilst not as unstable as when they are the driving wheels, as in a Mk1/2 Escort or Transit there are many ways to 'frig' a solid axle to have better suspension geometry such as DiDion or Watts links and/or multi link location and coil springs.

I've seen RWD Transits with full 4 link location of the rear axle, and even one with Sierra subframe/diff. Connect - how about putting in mounting points re-inforced to current load points so the SLA FRS rear subframe with hubspacer to increase the track to match the Connect. All the suspension forces apart from the dampers are contained within the subframe.

Has anybody done a rear subframe from a Ford FWD into an earlier car or van ??

Martin