Has anybody on here done this conversion? I believe it possible to use all the Type3 or Beetle IRS rear suspension.If it's possible,can the Beetle IRS jigs be used? I think the Bus torsion bar tubes are much larger diameter than a Beetle,so how is that issue got round?

There is a split screen kombi running around down this way that uses Beetle IRS arms for the IRS conversion, it is not ideal, he has replaced the rear wheel bearings a few times, also it is very hard to position the brackets correctly on the Kombi torsion housing to get the camber right.

Do it properly and use a kombi IRS parts

You can buy a kit from India automotive or creative engineering or use a 68 buses IRS running gear

https://www.indianautomotive.com.au/collections/suspension-lowering/products/...

https://creative-engineering.com/product-category/rear-suspension/irs-kits/