Stall and Shift RPM Question.

Thanks to both of you. That is great information.
It was interesting to me that on the launch, there was no wheel spin however, 20 feet off the launch pad when it started to pull hard, bingo, right rear spun like I was on ice.
Gears will be this weekend I think.
If they go smooth, I will pull the dizzy and start the weld, grind process.
If as you say, I want to be in the 36-40* total, what should I limit the mech adv to?
My understanding is, I want as much initial as it can stand without detonation and without hot start problems fighting the starter. When I find that, do the math.
All in (36-40) minus initial = max mechanical.
i.e. (these numbers are just so I understand the math, not actual)
38* All in
18* initial
38*-18*=20* max mechanical.
Is that correct?

Yes!
I would start with this:
34* All in
18* initial
34*-18*=16* max mechanical.
This starting point curve will allow you to sneak up on the initial without detonation.