I have a heavy 4 bike hitch mount bike rack that will even pull a trailer but I got a new bike and I wanted something that would go on and off easily and allow the tailgate to open once the bike was off. I couldn't fine anything I liked so I "created" this rack out of spare parts for other racks.
I bought this rack extension for $65
http://www.rerack.com/inno-inh306-tire-hold-3rd-bike-add-on-return/
and a 2" to 1.25" hitch receiver for $15 and I had the perfect bike rack for $80.
http://www.harborfreight.com/2-inch-to-1-1-4-quarter-inch-hitch-adapter-65024.html
Hope that ideas saves you a few bucks!
Matt