steve I see u have not used the search at the top right of the page but!
to answer some of you questions, it is not your tranny it is your the tcu that controls how soon/slow/fast or hard your transmission shifts.
I am running a stock/rear with a wavetrac .and have for the last 483 blast down the 1/4 mile.
to change your gears in the rear you need the diff,& a tcu made to your S/N and year
I have diff's for sale 3.07,,,3.27,,,3.46 and those are the gears that you have a choice of your car either has a 3.07 or a 3.27 in it the 3.46 with wavetrac and tcu

the cost is $3780.00 , 3.07,,3.27..or 3.46
that includes Diff, TCU, Wave-trac, and shipping to you, in the USA ready to install .
core charge is in that price. for $3780. you keep your TCU and Diff (if u ever want to go back. if you want to trade in your diff and TCU, the price drops to $3280.00
if you already have a wave-trac and I can use it, and trade in your Diff &TCU and wavetrac , the price drops to $2280.00
any questions pm me , I have one 3.46 left. jim