I'm fairly confident the L.OC was an early Low Compression abbreviation. There was an A stamping for .020 O.S. cylinder bores. I once had a 76T HP E (cast crank engine) from a police car that had a sideways F mark on the pad. I wish I had pulled a piston and rod to measure before I traded it off. I suspect other alphabetical markings are indicative of other bore over sizes, but were stamped sideways or backwards to prevent them for being mistaken for the letter year stamping. Darksideracing shows B as .010 undersized crank journals but other sites show Maltese cross with an X for rods and mains, RX for rods, and MX for mains .010 undersized. I don’t know if you had planned on tearing it down, but if it has the stock internals in it you may be able to measure and share your findings with us.
