Hi,
We managed it fine and I took a fair bit with me. See the thread for our road trip, some things you may find useful for items thats are a must to take.
viewtopic.php?f=13&t=48224
The obvious being you can't fit a suitcase in there, so we took big overnight sport bags. If the missus is like me, she needs an outfit for every day, but this is easily achieved by taking loads of nice shorts, as your travelling in the car you wont need much attire, then just a few nice outfits for the night.
We also put the presents from the trip in the little "hidey" hole behind the passenger seat.
I hope you have as much fun as we did, its pretty breathtaking
Cx