You
MUST use the cam gears from the Bandit. The GSXR has a different chain & sprocket arrangement. (You'd have to have a GSXR crank to run the GSXR chain & cam sprockets.)
Most folks doing a cam change use the 750 cams, but the principals should be the same. You'll save a little of the bottom end if you keep the B12 exhaust cam at the sacrifice of a couple-three HP on top.
If you want more torque (bottom-end & midrange), a big-bore and/or high compression kit is gonna do that for you. Gixxer cams are more for HP (top-end). You can get a good idea how this works by looking at these charts from Holeshot
(Click here). These start with a B12 with his 11:1 pistons, headwork, stage II jet kit, 5* advancer & his slip-on and then adds a GSXR 750 intake cam, then his full header system. The next set of charts compares this last setup against the same mods, but with his 1216 pistons. You'll see quite a jump in torque across the board with the 1216, but peak hp isn't much more - and happens at a lower rpm.