My roof rack came off of a '91 Olds Bravada (Yes, that is the first Gen s-series styling and a four door)
At the time there were none of the '94+ s-series in the salvage yards around my area.
I was looking for the newer styled rack , which is exactly what they ended up putting on the ZR5 when it arrived.
Any of the roof racks are easy to shorten, The rails in which the bows slide , are a formed or extruded piece. You can think of them as just a spacer between the end mounting pieces.
The Bravada rack that I took off, did not have the plastic removed from the double stick tape used to seal and mount it. I could see the red plastic showing, so that was definitely a plus.
Mine has the rails in contact with the top of the cab the entire length of the rack. The curvature of the tops were a little different so, I put a slight bend in it to match (test fit a couple times). With the Gen two racks the feet on the end pieces are the only part to touch so there would be no problems there and a much easier install.
Another advantage to the newer rack is that the water is not trapped by the rails like mine does. However I am very happy with mine. It is just a little different , and most people would never know it wasn't stock. (easier to find in the parking lot too, with that extra bow)
If you have the opportunity to remove the rack yourself at the salvage yard you will get all the hardware you need for sure and see how they mount it from the factory.
Mine mounted with eight "Nut-zerts" and the double stick tape.(available at a hardware store , good automotive tool supplier or any large truck repair shop should have one)
Nut-zerts are a threaded insert for a blind hole. It is kind of like a pop rivet. Only instead of a pin that pops it is threaded and has a section that crushes. You drill a hole that fits the insert closely and using the nut-zert tool crimp it pinching the body panel. I used large flange aluminum metric threaded nut-zerts , so it would match the stock hardware.
BOY this is getting pretty long winded, sorry
I don't remember exactly how much I cut it down, but I think it was about 8 to 10 inches. A hack saw worked fine , then filed it a bit to smooth the roughness and touched it up with some semi-gloss black paint and a brush. The finish wasn't harmed but I wanted to make sure the end that was cut was sealed to prevent any oxidation.
Once cut down I assembled it ,measured about fifty times to make sure it was square and centered. Then marked the holes to be drilled. The holes only need to go as deep as the Nut-zert, so do something I did not. Wrap a bunch of tape at the depth you need, around your drill bit to act as a stop so you don't drill through your headliner (I almost made a mistake when the bit grabbed) You may drill through the supports that run under the skin of the top , don't worry that is OK.
Once all the holes are drilled use some sealer, I use Permatex#2 since it stays pliable, apply a light bead to each nut-zert to help seal and crimp them all. Then test fit the rack again starting all the bolts to make sure you don't need to file a hole a little to get the bolts started and that it sits down flush to the top.
Next step , GET HELP! remove the protective backing from the double stick tape and carefully set it on top lining the holes up. You MUST get it right the first time there is no going back.Once that tape is down it is stuck!
Apply some more Permatex to the threads of the bolts (screws) and tighten them down.
If I remember right I had $25 in the rack (removed myself) , Bought another bow at a different yard for $15 and about $5 worth of hardware.
You might have a bit more if you need to buy a tool and some tape.