Since yours is a "street" car, I'd say a realistic number to shoot for is 10-12% "observed" loss.
In other words, see what the calculators show for 440-450hp(for your 500 std corrected hp).

Just the fact that your converter is probably 1000 less stall than what it would be if it were a race only application is going to impact the results, and what the calculators show for power.

My friends motor is under 500hp, and the car weighs 3450, and has gone 10.60's and 126mph at a few different tracks in decent air.

It is possible to beat what the calculators show for power, and most Stockers and Super Stockers that run in that one second under the index area are doing it........by a fair amount.

Another one that I'm sure of the data on........ 3650lbs, 470hp, 11.19@119+

On this one, the ET(514hp)looks way better than the MPH(478hp),mostly because the converter is too loose and the motor is driving through it in high gear, but the car still leaves pretty good with it(1.50 60').