I made dollies for my husband, for his attachments. I just used pallets, swivel wheles on the corners and most importantly one in the center of the pallet.
I had a bit of a height problem after i put my 47" snowthrower onto a dolly which I'd made out of pressure treated 2x8's and 4 rubber wheeled casters rated for 400 lb. each. My JD 2320 was about 1" too low to engage the quick attach to the bracket mounted on the loader. Solution? Put 2 short pieces of 2x8 board onto the floor in front of the wheels which allowed me to line up the attachment and then drive the tractor up onto the board to gain the height differential.