They do make 911 replicas to fit ontop of VW chassis, pretty well built cars too. But if I were to modify a metal bodied 911/912, I'd prefer the Porsche chassis anytime over VW's. So it'll just end up a customized Porsche, not a rebodied VW (if it was up to me).
I know I'm getting a little picture happy, but I just designed two more concepts. Look how great 17" wheels look!
and
Sorry, I know they are a little dicey but you get the idea.
There's a current UK company that makes convincing replicas of 911's. I can't find the link anymore but here's a few other ones:
----------------------------------------------------
Indy Exotics - phone: (317) 784-1119.
15512 Churchman Avenue
Indianapolis
IN
46203
-----------------------------------------------------
Diaspora S.A.
Circuito Del LInce Pte.,
3302 Cuidad Bugambilias,
45090 Zapopan, Jalisco, Mexico
(3) 684-48-43