The back of the crewcab has the same floor profile as a a regular cab. As far as I can tell, the only difference between the crewcab rear seat and a regular-cab bench is one uses fixed brackets, the other has sliding tracks.
The Suburban has a dead-rise of 6-8" from the passenger floor up to the height of the load floor. The backrest of the middle seat mounts to this corner with a piano hinge. Judging from the door pillar, the seat sits a few inches further back that they do in the crewcab.
The floor under the rear seat area of the Suburban is flat, whereas the crewcab floor is pushed up for fuel tank clearance. To use the Suburban rear seat, you would need to re-work the floor considerably. You may want to look at the seats in some newer crewcabs that are designed to fold flat into a load floor.
The rear seats on my '91 crewcab, and on my Dad's '79 crewcab both fold forward (backrest only - to about 45*).