Hi, I have a 64 beetle with the original 6v gearbox in it. It has a 1300 12v engine at the moment, but have a 1500 engine and gearbox to put in it. What do I need to change on the 1500 gearbox to fit it in. Any advice would be much appreciated.

No need to change anything if the gearbox is out of a 1500 type 1.
The 1300 and 1500 12 volt gearboxes have longer axles than the original '64 gearbox, which widens your track.
Not a real problem though.
Cheers Dave