Engine Test Stand using K member?

You would still have to fabricate mounts for the rear of the engine, or have the transmission attached and sitting on the ground.

Yeah I think I would mount the 4 speed gearbox and fab a support for it

I have see run stands (not based on a k-frame) use a bellhousing only. There is an earlier bellhousing (not A-833) that could possibly be a cheap score.