If you put a motorcycle style kickstand on your bike (double kickstand) you don't even need a rack.. I have an F150 LB and just set the bike upright in the middle of the bed, and use two ratcheting straps (like $10 at HF), and wrap one around the front of the frame and the other around the back... and just attach them to your tiedowns in the corners. Never had a single problem. It does take a few minutes and if you have two bikes it's a little more complicated.
The other way is to lay 2x4's in the notches across your bed, and attach a pair of 2x6's lengthwise and upright for each bike.. You'd still have to strap them down.