Passenger Seat into Driver's Seat
1986 325 ES: Here are the basics for seat removal and conversion. You'll need a 17mm socket, possibly a 17mm swivel socket, and penetrating oil. Start by moving the seat all the way back on the rails, and removing the black nut caps. Then, remove the front two nuts on the rail. Now slide the seat forward and take off the back two bolts. This is where you may need the swivel and an extension. If your seats don't fall forward (like say in a 325 four door) you'll need the swivel to get the rear bolts out. Or if your two door's seat no longer falls forward, but slides on the rail, you'll need the swivel. If your seat does not move on the rail, most likely the metal bar that connects the two releases on either side of the rail under the seat, has fallen off, (thanks Kevin)! Pull up on the one side where the handle is, and use a screw driver to release the one on the other side, and your seat should slide forward. Be sure to check that there are no debris in the rail. Now to the conversion.
Here is what I did. I found a decent passenger seat in the junk yard. As we all know, a passenger seat is usually in better shape than the driver's seat. The seat I found was a stiff stock seat that does nothing but recline and slide back and forth: it came out of a 4 door 84 325. The driver's side in my ES had this great custom seat with all the bells, whistles, adjustments, (including heat I think), but it was trash. Not only had a dog chewed it, but the guy who had the car before me was like 280 lbs. Anyhow, I could barely see over the steering wheel when I sat in this worn seat, and I'm 5' 11" tall. I took the 4 door passenger seat from the boneyard and coverted it to the drivers side. Everything fits and operates, even though the recline handle is now on the ram tunnel side. The only mode I had to make was to snip a bit of the cover that goes over the recline mechanism in order to sneak the seat belt by and bolt it in. So now, I have a nice stiff driver's seat that cost me 40 bucks. Of course, I can't fold the seat forward for rear passenger access, but it will slide forward and there's enough room for someone to squeeze in, and on my passeneger side, the seat still fallls forward for rear seat access. (BTW, my ES passenger seat which I left in, did not slide on it's rails, but I gangsterized the rod from the removed driver's seat and now, it's all good). So, if you need a new driver's seat, and you're on a budget, you can convert a 325 four door passenger seat, into a drivers seat for a two door. I'll keep scouring the yards for those 40.00 black leather top of the line, direct fit, BMW seats that are out there somewhere in the universe, but until then, with black seat covers, I' ll be riding high in the saddle and seeing over the steering wheel.
I hope this helps someone