The Truxxx kit (the rear spacer) would not work with factory air ride, so it would be a good time to switch over to springs. You can usually find them used here and on ebay cause a lot of full suspension system kits come with replacement springs. I got my Truxxx keys and spacers (with free shipping).
http://www.autoanything.com/suspensi...A5218A0A0.aspx