Help with engine numbers

PM 318 R 2257 2858 is the engine serial number.

It was stamped after the engine final assembly was completed.

(this serial number should not be confused with the partial or full VIN stamped on blocks for the years that was done)

PM - Assembled at the Mound Road Assembly plant.

318 - 318 cubic inches

R - Regular fuel recommended

2257 - October 2nd, 1967 final assembly date (1968 model year)

2858 - 2,858th engine assembled at the plant above on the date above.