Stock width spring in the front be it a lift spring or not is an assembled width of 3.5".
Our shackle eye hangers are set up for a 3" assembled width. So, if you put a heavy washer on one end of the shackle sides you'll make up the difference and be right on track.
If you want to use the heavy washers in conjunction I'll weld them to the shackles for you free of charge.