I just changed the transmission and the cv shafts, serviced the clutch, new pilot bearing, etc.  
Wanted to start, it would not turn over.  I thought, it’s the battery.  Not.  
Went to see if the engine turns by hand and it would not move.  
The clutch works fine, the starter clicks but can’t turn the engine.  

I can’t imagine what causes it.

Anyone has an idea?  

Zoltan