What year 350 engine

[his15153]

I have a 1969 Chevy C10, and I am trying to find out what year 350 engine is in it. I know it is not the original engine. Also, I am pretty sure it is newer than 69. I tried to find the serial number, but can't seem to find it. I saw online that it is on the drivers side near where the transmission bolts onto the block. I've looked everywhere that I have access to, but didn't see it.

I need to buy a new power steering pump, and so need to know what year to purchase it. The power steering pump in it currently is probably not the right one, as it has fitment issues.