If you are spinning bad, don't do this, but in order to get the stall speed higher, do not power-brake the car. You can "flash" the stall speed higher by accelerating the engine into the converter rather than loading it up. Just leave the engine at idle in 1st gear and floor it. This gives the engine a few revs of almost freewheeling to build momentum before the converter tries to slow it down. This will cause more wheelspin though.
The same concept works with manual trannys too. Many people hold the engine at a launch rpm, for a better launch, you want the engine to be accelerating through launch rpm when you let the clutch out, not idling at launch rpm.
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67 Fastback - Arctic White Pearl paint
351W ,Trick Flow Aluminum Heads, Edelbrock TorkerII, Carter 750 CFM, Comp. Cam 477/510 219/233@.050, Performance Automatic C-4 Trans, 3.55 gears, Front Disc Brakes, 1-1/8" Fr. 3/4" rear sway bars.
My 351W Fastback