M-code Dart, Barracuda 69 440 bare block

I've never seen a block like this in a M-code car. The only blocks that I have seen like this were in late model C-Bodies in fact I have one out in the garage but I don't remember what year it's from. My car has the original motor mount that required me to drill and tap the two oil pump bosses. The real answer to this might be the vin number but if it's only partialy stamped stamped it could be from a 6 pack car.
This block, is an early casting for the 69 model year #2536430-10, casting date 8-9-68. The 2 bosses in front near the oil pump area are drilled and tapped from the factory to accept the M-code mount. The factory cast more of these early blocks than were actually used in the 440 A-bodies, the leftover units I would assume, went into other cars. In Plymouth's case, which is where this one was cast would have been the GTX. which is what this one was originally installed in, casting, and assembly date is way to early for the 69-1/2 A12 six-bbl cars. vin# on the side pad is RS23L9G162589. This engine was originally painted turquoise.