Yet, another 6 Lug Rotor ??

[70GMCer]

OK, this most likely has been asked before. What Chevy/GMC trucks from 73 thru 87 came with 6 lug front rotors that are 2wd? I'm getting ready to do a drum to disk swap and already have all the other parts for this job, and need to know this. Should I be looking for the 2500 series or is there a 6 lug 1500 series? I've also heard on here about a 1990 3/4T 2X4 Light Duty rotors work. There is no listing that I can find for a 1990 Light Duty truck. What series was that? I have read on here about the thickness of the late model rotors being different also.

All the part books never say if they are 6 or 5 lug, and these parts store clerks don't seem to have a clue when I call, (Advance, Autozone).....

thank, steve