Actually, after reading this current carby thread http://www.camaros.org/forum/index.php?topic=7068.0
in the decoding board, I realised I wasn't calculating the dates quite correctly anyway.
I was assuming an alternator date that had to be slightly before the engine date.
This assumption was incorrect as the engine date is for only the bare long motor [minus carby, alt, dist etc.]
Whilst 7L30 is valid, it could have been anything up to about 7M8 or even later - i.e. after
the engine date would also be valid [maybe more valid?]
In fact, depending on the exact time line between fisher body building, engine final assembly and chevrolet vehicle assembly, an alternator date that is in the same week as the fisher body date may also be possible.....