Hi Guys,
I built a car dolly out of 2x4s and 2x6s. I started out using pneumatic casters from northern tool and quickly switched to solid casters since the pneumatic could not hold that much weight. In the pic you can see the caster flattened by the weight
Here's a picture of the car on the dolly,
The frame sits on the cross pieces of the dolly. I put in extra bracing becasue i was paranoid.
IF i could re-do it, I would make the dolly shorter. I had to get a couple guys over to help lift the car onto the dolly. Although when I took the car off, I had the engine hoist hold the heavier end of the car. (rear)
Here's some pics of the dolly when I built it
I think i used 2 2x6's , 4 2x4s and misc screws and bolts. Should be under $100.