Re: 4L80E - attention George!
Still do the HD2. The only thing you'll have work on is the filter at the base of the manual shift valve. It will still work. You just have to use a belt sander and shorten the plastic filter some so the aluminum plug will seat far enough to get the roll pin back in.
There are a LOT of mods to do to the pump. It's all laid out in the HD2 kit. Big thing is KEEP TRACK of the valvebody parts when it comes apart for cleaning. There are 4 different variations I've seen. So take a pic or lay them out so they are NOT disturbed.
Check the separator plate. I've seen many of these where a check ball has busted through and stuck in the plate. If you see this or a plate that the ball has almost entirely worn the hole through, replace the plate using the transgo plate. It's almost twice as thick and it's zinc plated to prevent the checkballs from wearing through it.
You'll also need a short manual shaft. I have two of those in stock. If you go to the nats, the giveaway trans will be there and I'll show you what I'm talking about.
The late model 80s seem to all have the park neutral safety switch on the outside and the manual shaft is really long to accomidate it. This shaft is way too long and will hit the front prop shaft.
If you get a 4x4 model, make SURE it has a reluctor wheel for the rear TOSS sensor to get the output shaft speed. They usually do not have the reluctor on there. I stock those reluctors as well. It presses onto the rear planetary.
You'll need the wider stator support bushing I have and the no walk rear case bushing. Those really help prevent issues from arising later.