91 still has the GM column, I have a 92 out back with the same. I would go ahead and pull the wheel, lock plate, and maybe even the turn signals to gain access to the button or screw which retains the cylinder, because it slides out in the on position. Slide a new one in, problem solved... Unless the linkage to the ignition switch down on the column is busted, pewter gear and D-ring. Either way, once it's out, if you can work the tab down in there with pliers and find all your detents, a new cylinder will solve your problem.