1968 Dodge D200 with a 318 from who knows where

I found a chart if you will, online that has the breakdown for the number below the head on the front of the block, drivers side. Going by that number breakdown of PM 318R 25020444, this engine was manufactured or installed in 79, it was built in the Mount Road plant, it's a 318 that uses regular fuel. The engine block was built in 1968 and I don't care enough to figure out which day.
This means to me, at some point in 1979 they altered this truck, probably using extra leftover parts from who knows where.

SBM Castings (3)1.jpg