this guy has put in IRS from an AUII VCT XR6 as well as front suspension and VCT motor. This would also be possible on an EA-ED as the AU floor pan is the based on the same platfrom EA26.
I wouldnt even bother considering the BA as the suspension towers are different and there are major chassis changes in the rear. Plus the AU IRS is pretty good. Better than anything holden have ever put out there. No crappy squat as you get from the inferior semi trailing arm setup as on the VN-VZs.
I see that you want to attempt IRS on a wagon. Well thats one big job considering there is no falcon wagon with a coil sprung axle let alone IRS. You will need to do some serious re-engineering and I mean, more than your EL is worth unless you are an engineer yourself and write up your own compliance for the modifications. However the wagon is based on the LWB (fairlane/LTD) platform so there might be a way of adapting coil sprung rear from AU fairlane if they got IRS treatment as I only know of XR8, XR6 VCT and fairmont ghia.
anyways, hope this gives you an idea of what your in for.
Re: FORD FALCON AU LSD IRS DIFF CENTRE Fit into EF wagon
Thank for letting me know about Shane's EL futura Well done Anyway last my EB wagon had fitted rear sway bar from eb sedan so what i did is cut out swaybar mount bracket from sedan with oxy torch ,clean up and reweld back on EB wagon chassic frame and made up sway bar bracket to fit rear axle (weld)same as sedan that l able to bolt it on and modifcation swaybar by putting on hydraulic press on each bend to make swaybar narrow because was touching 2 rear shock absorber,s tubes until got enought clearest approx 15mm each side and this was done 4 years ago or 450.000 km and gave me no problem and handle extremly well and lot safer to drive ever on unmade road or winding road so why ford company didnt think that way speciality on the wagon .Early Holden kingwood wagon has fitted by the factory
Now l got EF wagon and will do the same in next fews weeks also will post photo when it finish however l will try to do my homework to find away how to fit Au LSD IRS Diff centre in next couple of months depend how much spare time l have