Mystery engine

I'll guess October 28, 1969, casting date? What numerals + letters are stamped into driver's front of block, just below head to indicate assembly date and plant,etc.? Numbers on machined pad above oil pan rail, passenger side? You beat me to it A56!
Front of block is PM 318R 30642144. With the chart you sent me looks like built Dec16, 1969. Bingo, built about six weeks after casting. Thanks again.