Another thing to keep in mind is that the holes to bolt them on might not be standardized. I have 3 Suburbans being used to make 1. The truck I am building had the chrome drip rails. The other two didn't. I undid all those stupid little bitty screws and took a set off the '89 which were body color. I painted them all up and went to bolt them on the '87. None of the 5 drip rails had any screw holes line up. I could start 1, but no others. I held the '87 rails up to the '90 and they weren't close. Neither were the '89 rails on the '90.
I came to the conclusion that the factory must have used the rubber gasket to glue the rails on while a worker installed the screws wherever they felt like on each truck.
If you go junk yard looking my advice is to make a cardboard template of your existing holes and compare it to any truck you think will donate.