360 block ID?!?

I bought a 360 short block and would like to find out what year it is and possibly what it came out of originally. The casting numbers are 3418496-7-360.

I decoded this to be a 71-74 block, but that is as far as I could get.

There is no ring ridge, shows standard bore pistons, and spins freely. I gave $100, figured I couldn't go wrong. Just want to know what I bought.

Thanks in advance.