Don,
Here's a try at interpretation:
3835913 = 54/55 235 head
Head date: 913 = Sept 1 1953 or 1963? (2 bolt valve cover(1953) or 4 machine screw valve cover (1953)
3764476 = 56-62 truck block
Block date: A88 = Jan 8 1958
217 in the engine serial number location on the block?
Some sort of replacement-engine code?
Maybe others can provide better information?
Is there really such thing as a from 56 to a 62 block? There is a caution notice in the factory shop manual, 1958 truck, page 8-10 to not install early 1957 mechanical tappets in 1958 six cylinder truck engines. So there is a difference.