Or you could use a sprinter 4 bolt output flange and adapt the end of a sprinter d-shaft to your existing short shaft, like Mr. sprinter 711651 did here on his 6 speed conversion: http://www.clubgwagen.com/forum/viewtopic.php?f=27&t=2913&hilit=6+speed+transmission+flange
Or fabricate one flange like Axle B. did in the UK: http://www.clubgwagen.com/forum/viewtopic.php?f=18&t=4784&hilit=flange&start=20
There are 2 flavors of MBZ drive flanges, the early type (roughly 1953-1996) and the late type (~1996-present, exclusive use of the 722.6 marks the change).
The early 'smaller' flanges came in several d-shaft bolt patterns depending on application (3 bolt for passenger cars, 6 bolt for van/early G, and 8 bolt for later G) but they all share the same output shaft dimensions of 29mm diameter with 27 splines. All 6 of the output/input shafts on a 460 are 29mm diameter with 27 splines.
The later 'larger' drive flanges also come in different bolt patterns (3 bolt for passenger cars, 4 bolt for sprinter vans, and the homokinetic flange for the G. *I think
there is a 6 or 8 bolt G flange that fits a 722.6, see FSM image here: http://www.neoriginal.ru/cat/mb/part__1_44W_FG_202033_23Y_GA_722631/27_095
) Im not 100% but I believe the larger flanges use a 34.6mm diameter 26 spline (same as G axle shafts), can you confirm Vadim?
This is the flange used on all modern MBZ transmissions (5spd auto, 7spd auto, and various 6 spd manuals).
MBZ still uses the 'smaller' flavor of flange for t-cases and differentials.