The left and right bases are not interchangable.
What is wrong with the seat? Why does the seat "not support me anymore"? Is the seat bottom broken where you tend to slide off into the door? The screws that hold the electric controls to the seat bottom may be stripped out or the controls may be tearing the upholstry.
If this is your problem, the sheet metal pan inside the seat bottom is cracked and will need to be replaced. They are the same for a manual or electric. I got a new bottom and back at the yard for 15 bucks. Once you get the bottom unbolted from the seat base, the padding and upholstry slide right off.
Does the base and back lean down and back on the left rear?
If this is your problem, the torque tube that transfers up/down drive from the right rear of the seat base to the left rear of the seat base has been twisted. Take your base out, remove both the seat bottom and back. Then lay it flat on a concrete floor and put a straight edge across the rear of where the seat bottom bolts to the base. Measure from this straight edge to the floor. The measurement should be the same side to side. You will likely find the left side to be low. You need to remove the spring that applies pressure to this torque tube. If you don't remove the spring first, it will really mess the tube up when you heat it. Then heat the rear torque tube and twist it in the direction to raise the left rear until the measurements from the straight edge to the floor are even. After the back is right, check the front, but that will probably be OK, once you get the left rear up. After I got mine straight, I split a piece of steel tubing and welded it over the torque tube so it would not bend again.
I had both of these problems with my 90 XJ seats.
The electric drive is to the right side of the seats, both passanger and driver. The stopped motor holds the right side up, but the tube has to transfer the load from the left side to the stopped motor to support that side. A large butt can wreck this tube.
