I strapped my combo to an old furniture dolly. HF has a cheap dolly for about $10, less on sale. An engine stand would be nice (if they made one to suit a whole combo), but the dolly is hard to tip and has casters permitting relatively easy mobility. It's easy to load that way too - it rode home in my minivan on top of that dolly.
The E36 pan sits in the middle, with the pulleys just in front of the crosspiece. The tranny sticks way off the other end, but it's very stable.
One of these days I'll install two locking casters, but for now I just use a couple of framing wedge scraps to keep it in the corner. That's only to protect my kids. It's so heavy it tends not to move on its own.