REMOVE THE BELLHOUSING FIRST!
The stovebolt engine is far too long to mount onto an engine stand with the bellhousing attached. It will tip over forward with very little effort, and you'll lose a bunch of toes, or worse. Also, you need to buy the heaviest possible engine stand available, one with a wide stance and four wheels, long enough for the front wheels to extend past the front end of the crankshaft.
Remove the bellhousing by first removing the flywheel- - - -there are bolts hidden under the flywheel that can only be accessed after the flywheel is off. It weighs 40 pounds or more, so be sure you have a good grip on the flywheel before removing the last bolt. Heavy gloves are an excellent idea.
I like to bolt a piece of 1/2" by 2" flat bar about 18" long with holes drilled at the ends across those two top bolt holes above the flywheel area so the engine stand brackets can spread out wide enough to share the load effectively. Use a stack of washers under the lower bracket arms to level the engine and make all the support arms in the same plane. Be very careful if you decide to roll the engine over to remove the oil pan- - - -it can rotate pretty violently if the stand pivot is too far off center. The stovebolt six weighs considerably more than a small block Chevy V8.
Jerry