Engine Test Stand
You just want to run the engine to break it in and check for leaks, then run leak-down and compression....Right?
I used to build prototype engines. We ran every engine after build to run checks and verify they did not leak.
After build, the engines were placed on steel dollys with 4 casters. The dolly had vertical bar stock (1 1/2' x 1/2") that supported the engine between the oil pan bolts. The bars were notched on end with a gap of about 1/2" so you could straddle a bolt head with the bar. These bars were horizontally adjustable by use of T-nuts in slots on the 1/2" steel bed plate the casters mounted to.
We used cut off bell housings to mount the starter motor. The cooling and electrical support systems were mounted to the wall. This was an industrial set up but the concept can easily be copied for home use. The main thing to remember is DO NOT open the throttle quickly or you will torque the engine and the dolly on its side. I have also seen a tempory hill-billy setup (in West Virginia) that used 2x4's nailed together to support the engine with trans attached, jumper cables from a pickup truck to get it started, and a running garden hose duct-taped to the water pump intake for cooling. It can be as simple or as sophisticated as you care, or can afford to make it.