Very possible I would think. Many items were dual sourced.I seem to recall my 1st 70 z28 was as well. Now that was 30 years ago (so memories a little fuzzy) and the car was a LA car (100% stock and I bought it from the 1st owner). Could LA have used a west coast part supplier so their’s were brass finish as opposed to back east?
The same block could be found on Corvette's also and through 1972. Should be many data points out there.