Just looked at the Service Bulletin and it specifically identifies affected engines by Serial Numbers, rather than identifying the crankshafts by Serial Number.
This is probably why the factory is not being particularly helpful, as it specifically states that there is no method to determine the fault in the field (I assume that to mean without teardown for inspection).
One of the Continental problems of the last few years, were caused by a tooling problem, which damaged the crank during manufacture. The Continental bulletin did provide a means for deciphering the Serial Number.
I'm not sure of the source of the problem with the Lycoming's, maybe a similar problem?
What is the turn-time on this project? How are Lycoming doing on handling this problem?
SB 550