I made one, primarily to test run a used '56 hemi I had purchased that was supposed to be a "good runner". It turned out to be in excellent shape. I had a couple of other engines I wanted to test, including a used '51 Mercury and a '51 Olds Rocket, so I made it "universal" with a rear mount from a Harbor Freight engine stand that slides back and for to accommodate different length engines and front mounts to pick up "Hurst-Style" saddle mounts. It has served me very well up to now, having test run 4 engines so far.
I will disagree a bit about the value of these stands. All piston rings available for most engines (including flatheads) these days are of the "Moly" type that break in almost immediately. I see no problem with starting a new engine with this type of rings and breaking it in on a stand. I also have no problem running a used engine that already has it's rings seated for enough time to get the bugs out and to see what kind of shape it's in (and even show a friend or two). I would much rather do the initial testing and running of a new engine on my stand, which has a full compliment of gauges, a good radiator with external fan, than laying on a truck tire on the garage floor. Should I build and engine with 50 year old chrome (or even cast iron) rings, I certainly would be careful to avoid glazing the cylinders. I really don't see this happening.
In my opinion, an engine test stand is real handy to have, especially if you are dealing with multiple engines or used engines. In addition, I really enjoyed building it. I do have one hint. Put substantially larger casters on your engine stand than on your cherry picker so it will roll under the stand. I used the same size on everything, and guess what happened.
