If you need to make your project car mobile so you can push it around the shop or squeeze it into a corner, check out Accessible Systems, maker of the Tire Skate. These guys are down in the great state of Tennessee, and make real high quality stuff. I couldn't believe how thick my skates were, or how nice the casters were. Heck, they even allow you to return the skates up to five years after buying them if you don't like them.
Two American thumbs up.
http://www.tireskate.com/index.php
Two American thumbs up.
http://www.tireskate.com/index.php