One question which comes up quite a bit is what the compatibility between seats are.  Just because all the seats look the same, it doesn't mean they are all bolted in the same way.

- 900s from '79 to '80 have a unique mounting system.  These seats have a front-mounted angle adjustment and a side-mounted slider mechanism.  This system is in common with later Saab 99s.

- 900s from '81 to '90 have a similar mounting system, except those cars which have passive (automatic) safety belts.  These seats will have a front-mounted angle adjustment and slider mechanism.  The driver's seat is anchored with two allen or torx bolts on the front, the passenger similarly in front but with a pair of locking nuts in the rear.

- 900s from '87 to '89 with passive safety belts share a mounting system.  These seats are secured front and back with a pair of allen or torx bolts on both the driver's and passenger's side.

- 900s from '91 to '94 have a similar mounting system, which they share with the 900s with passive safety belts.  These cars should also be wired for power seat adjustments.  These seats are secured front and back with a pair of allen or torx bolts on both the driver's and passenger's side.

- 9000s from '85 to '98 share a similar mounting system, which is the same as 900s with passive safety belts and those made between '91 and '94.  These seats are secured front and back with a pair of allen or torx bolts on both the driver's and passenger's side.

The rear seats come in five flavors:

-900s from '79 to '80 are unique.  

-900s from '81 to '93 except for convertibles will all be compatible.  

-900 convertibles do not flip down, and are narrower than standard 900s.

-9000s except for CD ("trunked") models will all be the same.

-9000CDs do not flip down.

-Finally, 4-door 900s feature a rear seat with a slightly different shape.  Although all 4-door cars can readily swap seats with '81-'93 2-door and 3-door cars, the outer leading edge of 4-door seats are rounded instead of squared.  This difference is purely cosmetic, although a 2-door or 3-door rear seat placed in a 4-door might made ingress slightly awkward.