I used mine last weekend, pretty sure they are M10 (like 99% sure), i pikied it a bit, i screwed in quality M10 studding on the top 2 bell housing bolts on the block. and then used nuts to secure it to the engine stand.
There is a stud that goes through the engine stand but not long enough to get a nut on (its at the front of the block at sump level, used to locat gearbox), so i just leave that one.
Then one the otherside you need a piece of long studding and 2 nuts to fasten.