These cars definitely have some body tolerances issues, but anything much more than a 1/2” out is pretty unusual. You’re saying there’s a 1.25” difference, that’s huge.
Before you can fix it you need figure out where the issue is. Are the perches centered on the axle? Is the axle centered under the car/frame rails? What’s the distance from the rail to the quarter on each side?
Time to break out the tape measure and figure out where the discrepancy comes from.
