This is not quite right. I was in the 317th TAW at Lockbourne AFB, OH up through 1969 when I went Guam.
At the time I left there was one aircraft undergoing the mod from three bladed props to four blades. It was in the Jumbo hanger. Don't remember the tail number
I went thru It one day while my aircraft 53-3134 was in phase inspection. And it sure was tore up, Props off, Sta 245 and barrels of sand in the fwd part of the cargo compartment.