Regarding VB upgrades:
I am going to be as honest and accurate as I can be.
The Transgo kit is good for all the AW4 valve bodies.
The valve body specific gaskets must be slightly different. They change part numbers from 2000 and up. Get the gasket that is appropriate to your year please.
I've never needed to source a whole complete valve body that wasn't in a transmission, but you can get parts from here: (for those that want to send in a core to minimize down time)
https://www.wittrans.com
As far as a complete working VB, I would suggest a used and already working VB. I have acquired entire transmissions from CL before for $50.
I just laid out a 2000 VB and a 1996 VB... NO DISCERNIBLE DIFFERENCE.
I should say this as well. This service is mostly figured out, but there is still information that is coming in. I am good at handling data, but the quantification of it is a process. I can tell you that if I make a mistake or do not have an answer for something, I will rectify it with you or find the answer. Some things take time. Some things take money. Some things take both.
That said, I am confident that ALL the VBs are swappable BETWEEN AW4s...however there are different VB gaskets part numbers from 2000+. Something must be slightly different between 1999- and 2000+, I just don't know exactly what yet. Despite the part number difference, the uppers and lowers of each VB on the 1996 and 2000 I just had next to each other show no real difference. Both have the same 4 digit casting numbers...although there is another number above (2 digit) that was different and casting dates were different. Every bolt location, every hole, every contour looks to me to be identical. Solenoids are slightly different in color, some have numbers and some don't...but they are definitely swappable. Merdock69 can confirm this.
I am 99% sure I have just visually confirmed that with Talyn's 2000 VB and my original 1996 VB sitting next to each other.
ALL SYSTEMS GO.