These were indeed surplus UH-1B (Bell 204) from Army inventories. At first these were aircraft already in Army service in theatre and later Army airframes in CONUS and transferred to Navy and assigned a BuNo. The Army upgraded to the UH-1C which had a vastly improved rotor system. Retreating blade stall and poor high DA performance was a big problem in the B - and HC-1/HAL-3 discovered the hard way.
But in true Naval Aviation fashion the crews developed very effective local training programs to counter and ultimately made the aircraft very effective in its mission. Through sheer force of will and trial and error.
The ultimate short cabin Huey was the AF UH-1P flown by the 20th SOS Green Hornets! GE T58 engine from the H-3 and H-46 with the dynamics and blades of UH-1C and a rotor brake and avionics upgrades.
