318 steel crank or not?
this is the way i have always told it.
All 273/318 are Internaly ballance and have NO off set balancer on the front, whether they are cast or steel.
All 360 are cast cranks and have a off set balancer for External balancing.
the 340,Up to 73, they were steel cranks and internally balanced,
73 was the only cast/ Externally balanced, with its own special offset balancer
I know this don't answer you Question completely.