I found it easy to do without a lift with the car wheels on the ground for maximum stability. Do one at a time so the body won't shift. Undo the body to frame bolt. Tap it out. Use a piece of wood as a lever between the body and frame and lift the body up just enough to slide in the new pad. Line up the holes and reinstall the body bolt. I did the A-pillars first, working alternately from side to side. I did the pads under the sheet floor/frame last. Other folks may have a different technique.
https://www.bobdrake.com/FordItem.aspx?Item=21A-5001