Yeah, early beetles are really getting rare now, no point wrecking one.
Wreck a 1972 or something while they are still common
By the way, is there any particular reason why you are switching to 12v? There is a hell of alot of misinformation about, mainley from people who don't know how elecrics work and automatically assume that because 6 is less then 12, a 12v system is 'better' then a 6v system. Iv ran various daily drivers with 6v and it was OK, even in winter, and I did some pretty big milage in one of them.
Also its not so straight forward. If you want to fit an alternator like you said, then you end up with a starter AND alternator, both of which are different to whats fitted(the alternator will foul the fuel pump too), etc etc, so thers alot of messing around and changing stuff to make your 12v gear fit.