@baqai
Bseries is no good for the type1 beetle, you'd be better off looking for a subaru impreza engine as it is more or less a straight fit to the car (requireing a little plumbing for the radiator)
as for the interior, alot is possible but at the end of the day most people woudl be happy with just a dash pad (like the 1302 and later models), anything non VW/audi/porsche fitted to a beelte is considered destruction & blasphemy.