the a/c is not controlled by classic
the stock setup grounds the ac clutch relay on passenger fender and is able to disconnect that ground at WOT
so to have AC work using stock harness you need to provide the ground for the clutch relay either with a ground wire at the relay or at the ecm plug at pin A2
if you want it to disconnect at WOT you could install a hobbs switch to cut the ground connection above a certain PSi
classic sequential wont have TCC control of the (lockup converter ) so if you have a lockup converter youll need to find a way to engage when you want it
a simple switch at pin F at aldl (the gm diagnostic connector under radio) to ground works
B2B boxes would have the esc , but depending on options a sequential may not have ESC
really not much difference in B2b vs sequential , sequential will idle smoother and a little quieter on the injector clicking
sequential can also have optional individual cylinder spark and fueling adjustment , b2b wont do individual
i have sequential w/ individual cyl in my 86 and dont use the individual control and it does seem to have esc, it will records and show timing drop if knock is detected but i never verified the timing is actually retarded .