Okay, that makes sense. The set I have without any mfg stamps are from a B body car with the outboard LCA tabs. So they could be as early as a '66 model with mid-65 production date.

I snapped a picture of a '70 LCA with the mid-mount LCA tab. Looks like this LCA was put together on the 237th day of 1969 which would put it into the beginning of the '70 model year. Thanks everyone for the help.