The torque converter has nothing to do with when shifts occur. Wide open throttle shift point is controlled by the governor in the transmission. You can get a kit from B&M that comes with different weights and springs that allow you to fine tune the shift points where you want them. Sort of like messing with the springs and weights to set your timing curve on a distributor.
Here is a great article that explains the process -
http://www.dragracingonline.com/tech...vi_9-bm-1.html