My longer term plan is to just shorten a H190 from perhaps an S12 or Bluebird. I've considered shortening an R31 BW78 but the factory LSD's are crap - stuck with spending $2500 on a KAAZ and only upto 4.11 gears are commonly available. I worked for a company (PRB/Birkin) that used BW68 diffs in their clubman/Lotus 7 live axle car and we had some LSD's custom built, but that too was stupidly expensive.
I have a lathe so I can clean up axle flanges if shortening a diff by that method. (I hate cutting threads - not too interested in DIY coil overs...).
Thanks for the heads up on engine mounts. I weld chromoly 2WD extreme off road buggies for a work, so I can get a little creative with the TIG/MIG to help the motor fit.
I may consider converting my 810 struts to 54mm Commodore tubes by boring the stubs out on my mill and welding the extracted Commodore tubes in. Considering running Commodore KYB Exel-G's at around $130 a pair whilst saving to buy a set of valved Commodore Bilsteins. I read the larger Bilsteins are great for longer events as they have a larger piston and don't overheat quickly - though currently my longest rally sprint run is around 7 minutes. Hmmm