I would not try and shorten the axle. You are left with all kind of tie rod and steering rod problems. I would work to get the tires off. The good news is ca is brittle and sometimes it breaks easily. If you get the tires off I would hollow out the center of the tires with a dremel tool. If these tires are like the old RNK tires, I think they are actually identical, there is rim detail on the back of the tire. If you grind out the tire to that diameter it will leave an edge for the wheel to sit on and you can shim out from the steering back plate to get the tire clearance closer to where you want it. The problem becomes steering rod and brake can clearance. Wide tires are always a problem.