I didn't know that B&M made a shifter with enough gates for a 6 speed auto. Or are you planning on running two B&M three speed shifters possibly a 4 speed shifter and a 2 speed Powerglide shifter?

 

Why not a good ole 4l80

 

Just kidding about B&M but I hadn't thought of the two shifter set-up, 4l80e would require too much surgery.

 

Why would a 4L80E require too much surgery? If you can put a TH400 in a '69 Camaro you should be able to put a 4L80E in one. A 4L80E is an overdrive version of the TH400. It's the same transmission just a little longer. Does the tunnel get too narrow at the end? You could always go with a T-56 6 speed manual.

 

I'm not sure there is presently a manual setup for one of these anywhere , it would definatley have to be done from the valve body since the ecm is inside the trans ,
And even then I'm not sure gm even made 6 positions on the gate for the shifter which would complicate things more ,I will do some studying on it but theres not much available yet that I can find .
As for now your best bet economically and performance wise would be a built 4l60e

 

th400 with a big nasty converter FTW!