Posts 8 & 9... Old tire works great. Back when I worked at a dealership (60 yrs ago), we had a couple mechanics that just ran them on the floor, no tire, no nothing. Never for anything serious... Just checking for leaks and noises.
My current 'stand' is a roll-around Chinese cart, sold by some vendor in HMN, intended for a sbc. I think at the time, they were on sale for something under 50 bucks (maybe 39.95). I modified the thing, both to have a sbc starter, and also, to fit a flathead ford. Turns out, to fit the flathead, I just turned the engine around 180 deg, and the mod to the stand was minimal to make the flathead fit. I've only used it a couple times, and although 'flimsy', it works. I'm not really recommending this, but for 'cheap', and for a guy that only might use it once or twice, it's ok. As noted above, bigger casters would be a plus. Heck, even if you don't use it as a run-stand, it's a cheap way to make a 'roller' for a flathead.