318 Identification

OK i am going thru my 68 Notchback and making sure numbers are good. Found all the numbers on the rad support and rear truck and they all match the fender tag order number. Now for the engine, i am not finding the stamp on the rear of the block but it is pretty dirty and not much room with the engine still in the car. I did find the front stamp under the drivers side head and the casting date on the passenger side. This is were my confusions starts. The casting date on the side of the block is 9-6-67 ok not sure if a block would sit that long as my build date for the car was 9-19-68. The stamp on the front is PM318R 2243 272? If i read the sheet correctly a P is a 79? but the 2243 is a 68 date code?
Looks good to me for an original for your car. PM is Mound Road plant and was used in both '68 and '69. (for the 273's also) The casting date is good for an early '68 model too. 919 is Sept 19th 1967, not '68. Also, in '68 the VIN was not stamped into a 318 block. Only high performance engines got that. In '69 they all got it.