How do you make a 3d version of the bentley cake?

How fast do you need it? If you have time, I highly recommend Mike McCarey's Cakenology DVD "Car Cakes". If you're on short notice, you need scale blueprints (possibly from http://www.the-blueprints.com) and a model of the car if possible. You use the profile blueprints to carve the profile and the top view of the blueprints to get your width and angles right. My first scale car cake, a Back to the Future DeLorean, took us over 24 hours to complete. I hope I have given you a good place to start.

oh wow, thanks for the advice, but don't need it until next month. I have just a little time on my hands