I just got done doing this job on my hydro clutch NP-435. Just glad I got to it before the temps got like they are right now! It's been lows of -5į and highs of 15į. I'm okay outside under and around the truck as long as it's in the 20s or above.
I haven't bled my clutch yet, and I just have a squishy clutch pedal. The clutch fully works and I can drive it, but there's no real firm return on the pedal. It just kinda eases back up when I let off. But it freely moves, and works.
When you put your transmission and engine together, what order did you do it in? Did you have the bellhousing on the engine or the transmission? Was the input shaft from the transmission already through the throwout bearing before it went together? Or was the bellhousing on the engine and you tried to "stab" the transmission shaft through the throwout bearing and into the engine?
The first option would look like this: (Granted, this picture was taken before I repaired the seized throwout bearing)
If it was the latter, I wonder if you knocked the throwout bearing off of the clutch fork, or to where it wasn't fully seated on the fork and is now binding.
Hopefully you don't have to pull them apart, but from having just looked everything over in there myself, I'm not sure how you could line stuff inside back up without doing so.