I have now built a pair of dollies for my JD 48 backhoe, and have the hoe sitting on them!
Here are some pics to prove it happened. I was concerned about the height of the dolly to go under the frame. I needed to maintain enough room to drop the hoe out of the attachment hooks. Consequently, I chose 3/4 inch maple boards, to give me strength without so much thickness. That dolly is 28 inches by 16 inches. I used 3.5 inch casters on that one, rated at 230 lbs each.
The second dolly (for under the bucket) was 18 inches square, made out of 2 x 4 and 2 x 6 lumber. I used 3 inch casters on that one.
It takes a bit of push, but I can roll it by myself around the garage floor. I have some stuff stored under the platform behind the hoe that I want to be able to get at.
Note that I chained the dipstick to the transport pin in the boom, so it won't leak down and spread. I also have the stabilizers tied up, so they should stay put.
I mounted an 850 Lb counterweight on the 3 PT hitch, which, along with my weighted rear tires, ought to be enough ballast for snow removal duty. The rig is a good deal shorter now, with the counterweight in place of the hoe.