AFAIK the axle code per the build sheet should be the last 3 digits of a 7 digit part number with no alpha. For example, on line 4, "REAR SPRINGS" the entry is "132", an abbreviation for 2835132, the part number of the spring assemblies. This is a factory only part number that will not appear in a parts counter book.

But I only have a '69 build sheet, not '72. My WAG is that "670" is the build sheet axle code, which would make the "H182" a head scratcher as far as a date code. 18th day of February?

In all examples above, the axle code is on the driver side of the car with no alpha. And the axle assembly date codes are also stenciled on the driver side, always with an alpha and a dash between the month and the day. It can also be said that the examples vary in their details, and that there are likely other cases that don't agree with these examples at all.