I put 4 under my sons 67 Dart 270. Could NOT roll the front end at all. The rear was movable but not smoothly.
I took 5 of the $12 wood movers dollies, took 1 apart and put two more of the swivel wheels under 4 of them to make four each into 6 swivel wheel ones, and this works well.
The steel ones I use for my engine blocks. I just welded some steel strap on so the blocks sit square. They roll around real well. The movers dollies ?   So the wooden ones have a better quality caster wheels ? With 6 castors under then yes.
Retired, US ARMY 1973-1994
ASE mechanic, Electrical 1994-1997
Retired GTE/VERIZON/FRONTIER 1997-2015
Posting cheap tech help (CRAP) here since Nov 97, 1000's of posts, some may be good.
03 Suzuki Burgman 650(Burger King) Scooter
65 Formula S Cuda
78 Little Red Express Truck
98 Buick Regal (wifes car)
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