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.