Hold on just a second. If my sources are correct, then LBug boxes are pretty well as strong as an 091 2l box standard. Apparently they had very similar sized shafts and bearings in them. Kimm from Indian was telling me this. The only real compromise will be that of CVs. However, Bajawes has a way of converting CV flanges from beetle to kombi with a bit of simple maching and redrilling.
Check this page, There's technical drawing in pdf to show you how,
http://www.offroadvw.net/tech/
I'd be interested to know how this goes. The only real drama I see is how you're gonna hang the box in the Kombi engine bay.