I use these for my SPF. Get the ones that allow the heaviest duty ( I believe 10,000lb). Smaller wheel / weight ones will be cheaper but its also harder to push the car around.These will have better casters and the car will roll with a simple push. I usually just grab the front or rear bumpers and roll it. I dont think they have a lock but move the car next to a wall of put a 2x4 down as a spacer.
http://www.sears.com/merrick-machine...6&blockType=G6