Is there a difference between longboard and skateboard wheels, as far as dollies are concerned? All the posts I found in the archives refer to skateboards, however all the soft wheels I could find are made for longboards.

Are these (http://stores.ebay.com/Cheap-Sports-Stuff_Skateboard-Wheels_W0QQcolZ4QQdirZ1QQfsubZ5575850QQftidZ2QQtZkm) acceptable, for example? Is the thread size on these things standard, so I can insert any old pair of bearings, or do I have to match them to the wheels?

Back when I used to skate, we didn't have a special name for longboard wheels.

Anyway, what you would want for a skate dolly would be bigger, softer durometer wheels. 84 duro would probably work good. The ones in this auction are 97s, which are super hard. 97s will roll longer, but be more likely to transfer vibration from the track.

I really know nothing about skateboarding...Does that mean the thread size is standard? The wheel auctions do not include bearings so I do not want to have find an obscure-sized bearing.

Well this is what the owner, Rich, had to say:

All longboard and skateboard products are universal fit. All bearings fit all wheels. The larger wheels are listed as being for longboards because it's extremely rare that anyone would use them on a regular skateboard. Skateboard wheels normally run up to 56mm. Anything over 56mm would really be too big for a normal skateboard, although I'm sure some guys try. I sell a lot of the blank blue, red and grey longboard wheels for camera dollies. It's quite common, and the wheels are just as good as the Kryptonics. The only warning, if there has to be one, is that all skateboard and longboard wheels are intended for use on boards weighing less than 250 pounds INCLUDING the rider. If you have an extremely heavy dolly, camera and/or operator, no skateboard wheel will hold up. Longboard wheels have an embedded core that will snap if the weight is too heavy. To avoid the risk, you might want to use 8 to 12 wheels. I'm sure you've already thought of that! FYI, softer wheels roll slower than hard wheels. If you need to move the camera in a hurry, you do not want soft wheels. If you're doing action shots or are shooting any type of moving subject you probably want harder wheels.

I just bought two sets (8 wheels) of 78a's.