I found a note in an old HOLLANDER:

Forged crankshaft used up to engine # HM340-3911-8000

H = 1972 model year
M = Mound Rd. engine assembly plant
340 = 340 cu.in.
3911 = engine assembly date - Wednesday 4/12/72
8000 = engine unit number

much later in the model year than I had thought

Just thought I would add some more info. The original TSB came out April 19. On May 10 a revised one was issued. I assume that is how Hollander got their info. A little bit of trivia; according to the TSB there was a warning decal on the production t/conv or flywheel but not on the service replacements.

From hamtramck historical;