I made a universal dolly out of wood that works for a variety of things. I used two 10 foot long 2x10's. I cut them to 6 feet long, using the remaining 4 feet for the ends. The 4' x 6' size will fit into the back of most pickup trucks if necessary. I notched each of the 2x10's so that they align with each other, then bolted them together with lag bolts. I used another piece of 2x10 across the middle, securing it with lag bolts. Glued and screwed a piece of plywood on the top. A 2x6 laid flat across the bottom on both ends provides a place to secure the casters.
If I knew how to post photos, I would.
Dennis W. Parks
Author of automotive how-to books