The pictures might help. Why not just leave the spare tire on the top tube and put the toad on the lower tube. 4 down or dolly? This one is for 4000 lbs. but I'm sure you could find a 5000 lbs. if you looked around.
http://www.sears.com/maxxtow-70070-dual-hitch-extension-4-000lb-gtw/p-02866816000P?srccode=cii_10043468&cpncode=45-102266753-2&sid=IDx20070921x00003c