The collar matches the pressure plate, not the transmission. That's the message we're trying to send. The clutch fork pivot ball is in the exact same position on both transmissions, relative to the engine, flywheel, and pressure pate.
You might just make sure that slave cylinder bleed screw is angled upward when bleeding. Give it another bleed.
Sometimes people don't get the fork spring clips properly attached to the pivot ball and things get jammed up. Maybe make sure that the fork is right.
Just offering suggestions. There are no parts to suggest swapping to if you used all of the same parts from the 4 speed and did not change the pressure plate.