PN 3042489 is the number used from 1982-1988 and is for the G body, only.
PN 3042320 is the number used from 1980-1981, and was discontinued and cross-references to 3042489.
In theory, I can use either 3042320 or 3042489.
The 1978 (first design) and 1978-1979 PNs are different and do not cross-reference to the later numbers.
Unfortunately, the B body and F body parts are different.