Shifter wont allow manual mode

HI,
I am converting a Nissan Patrol to have a 6.6/Allison 1000 6spd from a GMC LMM 2010 2500HD, and have an issue with the shifter.

The stock Nissan shifter only has P-R-N-D, then shifts to the left for + and -

I have been told this wont work as the shifter linkage must go past D to enable the manual + / - mode of the gear box.

Looking at the drawings there seems to be a 4 position switch at the point where the cable shifter attaches to the auto.

Can any one tell if that next movement (I dont have on my shifter), is just to make the electrical switchs in a certain pattern or is the selector shaft actually changing some valve porting inside the trany as well.
If its just electrical beyond the D position, can you tell me which switches need to closed or open, when in the D position to allow auto manual mode, so I can mimic this please.

Thanks heaps in advance http://www.duramaxdiesels.com/forum/...lies/thumb.gif