I recommend starting for 4500-5000 upshifts.
Just finished reworking the TH400 Governor in the 63 Pontiac Gp.
Have 5700-6000 rpm upshifts.
It's very Violent though.
I like super fast of course but there is also safety.
Its kicking the tail end out on Violent high rpm upshifts.
Suspension being maxed out.
Weak old shocks.
Have a new set bought coming from Summit Racing.
57-60 mph 1-2.
80-84 mph 2-3:upshifts.
Wanted 90 mph 2-3 but has so much torque it pulls right past 90-111 mph in just 2 seconds later in 3rd high gear.
Just a warning be careful.
Best handling GM cars stock on True street tires is the Corvette C4 & Pontiac Trans Am 2nd gens.
Will apply to others like TH350 , 700R4, and 200R4.