All of the pickups for 1980 Grecos have a NXXXXX or a NXXXXX Nisshin Onpa (Maxon) stamp including the DiMarzio PAFs. The DiMarzio PAFs have "DIMARZIO PICKUPS" "MADE IN USA" imprinted on the baseplate.
From what I've gathered there are NXXXXX (1977-1982) or NXXXX (1977 and before) pickup serial number stamps on Grecos made by Matsumoku and Fujigen so the stamp isn't coming from the guitar factory it seems to be coming from Nisshin Onpa (Maxon). The DiMarzio pickups also have this stamp so it looks like Nisshin Onpa (Maxon) did the ordering of the DiMarzio pickups and put their serial number stamp on them.
Around 1982 the pickup serial number stamp is not used and this coincides with the Grecos having a pickup makeover and the Dry Z pickups become Dry 1982 and the U-1000 and U-2000 etc pickups end and the Sreamin etc pickups start. It also coincides with Fujigen starting to make their own pickups in 1981 so it looks like the manufacturer of the Greco pickups change from Nisshin Onpa (Maxon) to Fujigen around 1981/1982.
So I think your pickups aren't original.
Greco and Ibanez Nisshin Onpa (Maxon) pickup serial number format consisting of 5 numbers up to and including 1977. Ibanez Super 70 pickups have the same serial number format.
First number = Nisshin Onpa (Maxon) pickup code (1, 2, etc)
Second number = Year (7=1977)
Third number = Month (0=Jan ... 9=Oct then .=Nov, X=Dec)
Fourth and Fifth number = Day of Month (01-31)
Greco and Ibanez Nisshin Onpa (Maxon) pickup serial number format consisting of 6 numbers from 1977 to 1982.
First number = Nisshin Onpa (Maxon) pickup code (1, 2, etc)
Second number = Year (9=1979)
Third and Fourth number = Month (01=Jan ... 12=Dec)
Fifth and sixth number = Day of Month (01-31)