No speedometer since t-case swap and will not shift?

What confuses me, is that I have found a plethora of broken wires, corroded connectors, grounds on top of fresh paint from whoever "attempted" a half-assed restoration. All of this has been addressed, and absolutely nothing has changed. From turning the distributor once loosened, to get the timing dialed in for an "on dash" check engine light, the light went off. Been off since. But scanning shows codes from everywhere. The only other difference is, the trans is actually getting proper 12.5v voltage at pin E (pink wire) as when I started, it was down to around 5v. Yet still, all the symptoms are the same. (No speedo, wont shift) I can manually shift with almost no feel, but it is shifting, up to 3rd. And of course, down shifting manually works as well down to first. Lights all work, every gauge works, but the speedo. I always disconnect the battery for any electrical work. Bizarre, isn't it?

As I just stated eariler today, I did that already. I understand and appreciate you trying to help. Ive owned several of these 96-98s, and have never encountered anything like this. It would be quite an accomplishment to solve this issue, with how much I am already invested in it, as it seems rare and impossible. I want the satisfaction of it getting figured out lol. Could you help me with what I should do next?

Yes.

You had me test the pins 17 and 18 (vcm grounds) on c3? I did. Not showing anything