I put 850 seats in my 544. I used cloth seats because I do not have AC and older cloth seats were in much better condition than leather. I should have taken the back seat as well - I later found a magazine article on how to narrow a bench seat. I found a wrecked car that had all the windows intact so the seats were in perfect condition. I paid $100 each.

If you check around junkyards you might find a good value on seats from a much newer Volvo.

Things are supply and demand at most junkyards, so middle age seats are the best value.

I ground the mounting points off the 850 seats and had aluminum bars (3"x 1/4") welded across the seat rods. I removed the 544 seat rails and mounted a piece of 1/4" plywood to the rail mountings - then I mounted the 850 seat to the plywood. I cut away plywood to give rear seat foot room, and made the front of the plywood neater, The result was a fat H shape, Then I fabricated a 1/4" aluminum plate in the proper shape and with the proper bolt holes.

After I was done, I found that I could have retained the side air bag as the seat fit and the air bag was not electrical. I used an electric seat and kept the controls separate, I can connect the controls to the seat and the battery if I wish to adjust the seat. I also found that the 850 seat has provisions to adjust the seat height by loosening 4 bolts and move the seat - this did take some of the height adjustment away.

BTW -Tthe pasenger 850 seat can be released so that you can get in the back seat - find a passenger seat that does this. I didn' even consider this when I bought the seats, PHEW!