I have replaced the front and passengers seats in my '95 850 with seats from an S70 (1998, I think). Here is what I learned.

The seats will fit correctly. Bolt holes line up, etc. The challenge is in the wiring.

The 850 only had a power driver seat, whereas the S70 had both power passenger and driver seats. The connectors and wiring already in the 850 wiring harness will drive the S70 driver seat correctly. On the passenger side, however, the only wiring for the seat is a connector for the seat heater with three wires -- black, green and a small green/red. The challenge is getting power and ground to the S70 seat so it will operate.

The way I worked this out was to use the 850 seat heater circuit that was already in place. If you look at the schematic, the heater circuits run through two switch sockets in the console. These sockets are under the unopened cutouts next to the shifter. If you remove the console and put a jumper between pins 3 and 4 -- make sure that there's a fuse in the fuseblock that supplies power to seat heaters -- the green wire will be at +12V. You can then splice this into the S70 connector, along with the black ground wire, and voila you have a working power passenger seat.

John Martin