G50 gearboxes...
The first G50 arrived in 1987 in the 911 3.2 Carerra. It was used throughout the 964 911 including the Turbo (965).
The G64 I think (I need to check up on this) is the 4x4 gearbox, the G50 is the C2 box and the G50/50 is the Turbo box which can handle 800bhp as standard.
They are huge! Mark Thruston cut out the centre section of the torsion bar tube housing just to get it into the chassis.
Kennedy Engineering should (again I would have to check up on this) make a conversion kit so you can use the gearbox with whatever engine you like.
If you don't intend on putting more than 350bhp through the car... I would stick with a 915 trans... just my opinion.
If anyone has more info and I've got some of it wrong... sorry
MG