Don't use the rubber cushions, the polyurethane ones suck as well. Instead, buy some steel strap the width of your springs and make some steel spacers if needed so your U bolts will tighten OK. Leave the monoleaf perches on-they'll work just fine. Use a carbide burr in a die grinder to open up the perch holes if drilling won't work for you. The factory style cushions cause too much axle wrap, and the poly versions crack under stress, solid steel works the best IMO.