Walt,
Some ideas, though I've never actually had the need to try them:
1. With the carb or venturi removed, visually note the position of the crank opening when you turn the prop up against compression in both directions. Do the same with a known engine. Compare.
2. Turn it over both ways for the feel and sound. Compare to known.
3. An engine is an air pump. It will pump air out the exhaust when turned in its proper direction.
4. Run it on the test stand.
Mike was focused on CL racing, including Slow Rat, for quite a while. So I would guess his 36 would be standard rotation.
Randy