if youre looking at swapping your air ride...strutmasters has their conversion kit for $500+ on ebay...
http://cgi.ebay.com/ebaymotors/FORD...odel:Expedition|Year:2004&hash=item2a0ded476a
http://cgi.ebay.com/ebaymotors/FORD...odel:Expedition|Year:2004&hash=item2a0ded476a