340 Casting Number Questions

I was ware that the 3 and 5 were the core bins numbered 1 to 5.Here's what my Chrysler Corporation Part and casting numbers book says:

casting #3418915- 1970-71 360 open chamber 1.88, 1.6 (J,Z,O)

casting #3418915- 1970 340 T/A open chamber 2.02, 1.6 (O, U)

casting #3418915- 1971-72 340/360 open chamber 1.88, 1.6 (J)