The back seat in a K5 is the same as the third row in a Suburban.
It is also the same(minus brackets) as the shorty bench in the Suburban as well.
The "score" is the brackets. Far fewer 3rd row/K5 rear seats are available today, and if you do find them, expect to pay, even if they are beat up.
http://67-72chevytrucks.com/vboard/s...d.php?t=698932