in the owners manual there is no back window slider as a option so i think they were all after market. do you have a owners manual? they're cool to have. some of the nice options to have were the locking dlove box knob, locking fuel door, locking antenna, clock that nobody owns, some of the common upgrades that dont require modifications are the datsun 520 metal dash top, 520/roadster inner metal chrome door pull handles, red hazard switch knob, 520 steering wheel horn ring, rear bumperettes. elephant oil cap, valve cover that says datsun 1600.
oh the dome light door switches are one of the best upgrades you can do.
the original radio delete is hard to find.
how about a interior pic of you truck and a under hood pic?