Whilst I have the heads off'n Boy's Ebony, I looked. Our engines are in fact non-interference.

Just by eyeball (wouldn't know how to use a caliper even if I owned one), the piston only comes within about 1/4 inch of the top of the cylendar. Rotating the camshaft till one of the valves opens alla way ... it protrudes into the cylendar less than 1/4 inch.

That's good enough for me ... which is good since I have no confidence that we didn't lose our timing reference when we pulled the heads.