Starion like IRS you referring to yes? well thats the only one I can think of as I havent seen the sigma IRS but also theres an evo all alloy torque sensing irs diff.

Either way the closest independent rear end we can go without too much fussing around is use the mono leaf springs, torsion beam and CVs and hubs from a volvo 360, a couple of pipes to attach from chassis rails to hold the irs diff, modded drive flanges to suit the volvo CVs or mod your choice of commonly attainable CVs and your choice of shockers or coilovers but latter no necessary as mono leaf volvo ones are bulletproof.

This is the way Im going but still deciding on whether to use a suzuki grand vitara, mitsu evo or other alloy cased irs lsd unit.