The driveshaft support bearing is a R12-2RS just like all bikes made up to date. It is mounted between a 1/4″ diameter split pin in the rear and the flange of the bearing carrier in the front. The carrier has a full 360 degree outside diameter instead of 4 flats like later bikes. It is fastened with 3 1/4-28 UNF bolts spaced roughly 120 degrees apart. The frame tube and bearing were drilled and tapped in assembly. That means the frame tube also has threads. The bearing support is not adjustable front to rear like MK3 and later bikes are.