I've tuned several th350's. I didn't plan on writing a book but I guess if I took notes it would be of some use to you.
What needs to be done is a test drive to see what the trans does. If it shifts too early at wot lighter governor weights need to be installed, then test drive again. If it shifts too late at wot the weights need to be made heavier. With each weight change a spring change might be necessary and the downshift rpm may change.
Changing spring tensions effect part throttle shifts and can seperate shifts or bring them closer together.
You might need to adjust the vacuum modulator because different governor weights and springs may have some effect on part throttle shifts even though the wot shifts are where you want them.
No one can give you specific information on exactly what to install and have you go out and see your trans shift exactly as promised, there are way too many variables.
I'm sure it could be done if someone tested everything with every possible rear gear and tire size combination And recorded the spring tensions of each shift valve spring, governor spring and weight for each combination.
It's far easier to just dial it in yourself. It can be done in a few hours as long as you have a good stretch or road to test it on, and a good selection of parts.Not sure if i understand the question now that I think about it, but here's how i answered it.