As far as i know, no one on this site has done a rb26/t56 combo, but i haven't really read too much in the rb forum.
I did a quick google search and found someone putting a t56 on a rb26, but it was in a 240sx. You might try asking the person on that site what all is involved. http://www.paintballforum.com/automobiles/153827-240sx-widebody-rb27-project.html
I think other than just bragging rights to say that you have a t56 6 spd, its really not necessary and just complicating the process.
Kevin