273 or 318?

Found a post that says:

PM = built at mound road plant
273
R = regular fuel
2849 - > 10k cal = Friday, May 16, 1969
0556 - Engine built

what yr is my 273??


Interestingly and maybe it started in 69, the stamping doesn't follow previous year codes
Thanks Dana67Dart! That confirms it’s the original engine.

Not afraid of getting dirty @Professor Fate, but the cars in a tight spot at the moment and it’s been 112 degrees all week. I was just trying to get some prelim info to make plans for the build after the summer heat.