I was happy to get my frame on the dolly as the weather here is gorgeous and I have been moving it outside to work on it. Rolling it back in on to the ramps of lift has been much easier than I thought it would be.
I went with these casters:
Heavy Duty Caster Set
The price was right and they work great, if you have a concrete floor. When my Wife noticed I had moved the frame outside she came out and expressed concern I would throw out my back moving heavy stuff like that. I smiled, reached over with one finger and grabbed the frame, then walked over to her, pulling it behind me. :)