I think you're right about the 216 being a 53 version.
The number on the 6400 is one of the later engine numbers that were production number and I don't have any listings.
1953 and prior years used the engine numbers for titling purposes, not the VIN. We used to have some real interesting times when we changed engines. In Colorado, we had to get a state assigned number that looked like COLO1234 and then change the title to show the new number. Trying to put in a used engine required removing the old number and getting a new number. You had interesting times when you tried to sell the vehicle, because people thought the truck was rebuilt.
Starting in 1954, the states went to a VIN and the problems with engine numbers went away. After a while, the manufacturers quit using sequential numbers and began to use the production codes like you are showing. The S designated the producing plant for the engine, 0627 meant it was built on June 27 and the A tells what the engine was.
I'll lok tomorrow at some books I have at work to see if I can find anything.
You may have gotten more than you needed here, if so, I'm sorry. Brings back old memories.
Steve Ley
