I mentioned you would need to be careful with the converter selection.

This is quote I saved from the PY site.

"When I redid the TH400 in my '67 GTO last March, I installed a GM6-HS converter in place of the stock GM6 converter. The GM6-HS is spec'd for an LS6 or BB 'vette application, according to the info I could find. I am no trans expert, but the stall speed is listed as about 1800-1900 rpm....a little higher than the stock GM6. It works better than the original TC with my 2.56 gears out of the hole, and it doesn't slip at highway speeds (2200-2400 rpm /70-75 mph. I could actually feel a difference, seat of the pants."

This is not a big change as far as stall speed but IMO would be perfect.