They can be hard to read, you have the block casting number. 2538030 is actually 2536030 though.
318 is 318 CID
5 means that the casting mold was on it 5th revision when this block was cast.
Time to look for some stamped numbers now, looking at the front of the engine right of the watter pump below the driver's side head is a series of stamped numbers. They may look something like FW 318 0000 0000 as an example.
Look for the VIN too, for most years it is on the passenger side of the block down low. What is the casting date on the block? It is on the passenger side as well in large letters.
Post the numbers you find and I can help you with them.
T/Ake care,
Barry