We mess around with a lot of things back a long time ago to slow down a 10.60 car the run S/ST(10.90 index) we ended up getting the largest ET reduction by over revving the motor from 6400 RPM to 7000 RPM shifts in 1st and 2nd gear scope
We tried taking timing out down to 28 degrees in two degree increments, we tried short shifting at 6000. 5500, and 5000 RPM and even shifting directly from 1st to 3rd shruggy
We didn't add weight though, didn't have anywhere legal to store it shruggy
Lots of ways to slow them cars down up Find out what you like and which works best for you up

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)