She's alive! Man, I missed my ride so much.
In summary, this week I installed new Dorman trans cooler lines, Sonnax pinless accumulator pistons, a new "Iso-Conv" valve, a new VB separator plate, and (over)filled it with Dexron VI.
I did not replace the accumulator springs, I did not drill the VB spacer plate, and I had to drain some fluid because I added too much. Whoops.
This thing shifts like a dream. With 130% shift firmness and no PWM, it feels as close as you can imagine to a 5-speed Allison. Short, firm, but not choppy shifts.
Definitely a messy and frustrating job, but it's very satisfying in the end. I am so excited to drive to work tomorrow morning.