Welcome to CHR!

Block is a plane Jane - nothing special from a truck.

As to the heads, both are small valve, i.e., 1.72 intake and 1.5 exhaust. The 3774684 is a 75cc chamber (probably the original) and the 3795896 was probably a junk yard replacement at some time as it has a 60cc chamber.

Unless you have some attachment to this one, it’s probably not a keeper. I would definitely not invest a dime in the heads as they are really basic, poor performers that are 50 plus years old.

My 2 cents,
Glenn