I've studied alot about the UN1 gearbox (in modified form the Lotus Esprit g.box). There's one link which shows the UN1 installation in a T3 bus.
http://www.stud.uni-saarland.de/~mam...-getriebe.html
Another one for the offroad guys.
http://www.theoffroadshop.com.au/ser...earbox_ren.htm
İf I were to use a vw engine in a midengine setup (for eg. in a 550 spyder replica) or build a tubular frame buggy, I would go for the UN1 instead of a 914 box. The regular R 21 box with the 3.8 r&P has gear ratios very similar to a Berg 5. However as Mr. Bott stated the fitment into a beetle chassis can only be accomplished with extensive cutting of the frame horns and rear torsion housing. A 915 box is definately a better option for the bug.
Cheers