In a beetle, it would be critical towards the rear apron, but not nearly as bad as a 911 engine; Width however wouldn't be a problem at all.
But I was thinking more about an application in a type 3 or a 411/412, where the extra length of the engine itself would be about the same as a stock type 3 of 4 engine.
There is a fast (cor)vair group on yahoo:
http://autos.groups.yahoo.com/group/fastvair/
Walter