Food for thought: I kinda had to go the OTHER way of all of this on my truck with a 4.10 posi.
2006, 4L60E, Z71 + 3in lift, 4.10 posi, no anti-sway bars, mud tires.
I had done all my transmission shift tuning on street tires with police interceptor anti-sway bars on a Z71 suspension. Retuning the suspension, and therefore the behavior of the chassis, demanded that I soften things up to maintain good driveability. Thankfully, things are a little simpler on my older ECU with juuuuust enough flexiblity to get things right. I gave it a little more freedom to giddy-up with the TCS mapping, which would upset the chassis without bars and the new blocky tread pattern. It wasn't just the shift mapping, but also the TCS mapping that made it work.
1st up-shifts really low, Like 10mph under 50% throttle. 2nd up-shifts about 20mph, and on into 3rd, 4th, and lockup by 40mph. Massaging those curves do take some work. It wasn't about "mo powah" as much as dialing in characteristics for my combination. 3.73-4.10 gears on a 6-10spd just make more sense, to me. It doesn't need to be geared to do 180mph. I capped mine at 99mph, the rating of the tires, and worked with everything under there.
I need my own build thread at this point. I went to some extent to tune the chassis and the motor, but in stock form. Most of my adjustments were due to how I changed the handling. Aggressive throttle tuning with an incredibly soft suspension just wasn't happy. Traction control definitely played into things.