My engine test stand needs are pretty basic. It gets used a couple of times a year at most. My space is limited, so I needed something that would double up for storage.
I use the simple SBC engine cradles that a lot of different companies sell (I suspect all made in China, then rebranded by others) like this:
https://www.ebay.com.au/itm/256067658152?epid=1643664753&hash=item3b9ed261a8:g:suwAAOSwtXtkqo2~&amdata=enc%3AAQAIAAAA4FJRBAO0sElxIDTuRtnJJtk8DTrqxPQXQ8VSKnTRRpjkouO%2B80zkg%2BBzaVL5xpxLD%2ByNNANWTIJEfuuIxYj5rv5HE9%2BExuufbl5O10auGOJXPxcrTrtcqGuVLQrD0jvUxF9KUcphgIKbqsaHYlQxbFotDSajTpflzc%2FhzGpTXndqiv3z%2BAFInAQEQxcHz5okZf5RzCB4UsTJ9ZIUBjzxsCrdU2lWpFBD5EQaBNjrqeKHvhcpR3tnWgV%2FlSaBsoBphhHfHri9H5xUJ0h7eQTapktcKBOywplgVsAQdyIxN89w%7Ctkp%3ABFBM2qro0Z5jNote that this one is expensive, as you pay for the Aeroflow sticker. Buy the same thing without the sticker and more than halve the price.
A piece of angle iron bolted across the front lets me pick up the two front engine mount bolts. Two galvanised right-angle brackets (from Bunnings) bolted to the rear sit under the sump rail. All up I'm in for under $100. I use this setup to store my spare/junk/parts engines - lets me move them around to get at "the one at the back". There is enough balance that I can run an engine only, or an engine and gearbox (though the gearbox wants to tilt down). They sit moderately close to the ground, and are wide enough that it takes a fair amount of effort to tip one over.
When they get used as run stands, I connect the battery via jumper cables. A couple of years back I got cute and bought battery cables from Supercheap, but that is overkill. A single wire to the starter solenoid (bare end... touch to the terminal to start) is needed - I use the "test lead with two alligator clamps" that I use for 12V troubleshooting. For fuel I run rubber hose to the carb, supplied by plastic bottle. I sling the bottle from the carport rafters with tie wire (the fuel setup is somewhat sketchy, but with care works). Short runs (a minute of so) you don't need cooling. Longer runs (more than a minute) I run the garden hose into the water pump, gaffa-taped in place. No thermostat, and a piece of 20" bicycle inner-tube used to direct the spent water away from the motor (el-cheapo fire hose). If I'm worried about oil pressure I'll fit a test gauge. Zorst out through the headers, no muffler (my neighbours are understanding). Remove the mechanical fan, leave the pulley in place.
I don't tend to do long runs, like the 20 minutes to bed-in a cam. Most of my stuff is "will it run?" or "playing silly buggers with some new carb setup". For longer runs, I put the engine into the vehicle (as the next stage is usually "it works.... test drive!!!").
Sometimes things don't go as planned. Testing a set of CHC fuel injection on a grey I filled the cylinders with fuel and pumped burning fuel out the exhaust. The pavers survived, but it took me a while to unclench. As a younger Harv I once helped dad set fire to a Mini as we were running the zorst straight out the head, no headers
I wear ear muffs, as doing dumb crap like running open headers sneaks up on you, until one day you keep asking people "what?" when they speak.
I get the fire extinguisher out and ready a few metres back from the circus.
I put a nozzle on the garden hose and pressure it up, leaving it near the extinguisher. Not great on a fuel fire, but if things get really out of hand it's good to prevent fire spread whilst the fireys come.
I limit the amount of fuel in the bottle to about 300mL.
Cheers,
Harv