I installed a 60/40 in my 88rcsb during my build, it requires some modification to the seat bracket on the drivers rear near the trans tunnel and some massaging of that area as well. I used seats out of a 95 Tahoe so I don't know what year seats you are considering? Any way here are the pics of the modded bracket and after I got it in the truck.
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This pic is before I massaged the trans tunnel
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Passenger side bolts right into the factory holes
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Done!
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I ended up pulling and selling this 60/40 and went with bucket seats and a console.
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Interior all done
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Hope this helps! GL