556224 3″ Diameter Caster Wheels (Set of 4) … $42.99 (as of 1-25-13) from Shopsmith
The new casters from Shopsmith are one of my favorite all time upgrades.
I pushed, pulled, and wrestled Mark Vs all over the country for 20 + years, over gravel, in and out of malls, hotels and fairgrounds. If these casters had been available then, I would have paid triple the price.
Simply put: they make rolling the Mark V EASY! Shopsmith says, on their website and in ads, that you can push the Mark V/Mark 7 around with 1 finger…all true.
To install, you will need to turn the Mark upside down (see my video link below) drill a new set of holes, and install the casters. The new casters come with a paper template to make sure the holes are drilled in the right place. (THIS IS IMPORTANT!)
The only difficulty I had was breaking loose the old nuts that held the old caster assembly in place…some WD40 a half hour earlier would have been a good idea. It took me about 30 minutes to install.
Video on installing the casters: http://www.youtube.com/watch?v=TQIPzhn3fj4