As the car flips at the climax of the movie, the left rear wheel entirely comes off the axle, yet, when the car finally settles back onto the ground, the wheel is back on.
Flipped shot: Right before you see that the El Dorado has been chained up to drag Boone's car down the road, we get a quick glimpse of the front of the Cadillac. The right headlight is supposed to be burned our (or broken) but it is working again and the license plat is reversed.
The film only reveals tight shots and glimpses of Fargo driving his car, so it is unclear exactly how he was able to drive despite his impairments. However, the way he is shown exiting the vehicle in his wheelchair implies that he removed the original driver's seat and somehow adapted the car to accommodate his wheelchair as he drove. So it becomes a mystery what Molly sat on when she climbed in Fargo's car and drove it after Fargo had exited and rolled over to Rennie's tipped-over car in his wheelchair, presumably to find a souvenir.