Group 24 was standard. I think 27 may have been standard for Hemis but I can't say for certain.
If you have the Track Sheet (aka Broadcast Sheet) it'll call out a code.
I don't think the CCA was all that great back in the day; FSM should list what it was but IIRC they were in the 500s.
For a non-restoration deal, I usually buy the most CCA I can get in a given Group.