Eryri have some details about the race here, which includes a list of control points and their OS ref.

I haven't done the race myself (although have run up Moel Eilio) and I drew this map of what I believe to be the route based on the descriptions. Can someone point out if/where I've gone wrong? I'm failry sure it's accurate up to Moel Cynghorion's summit, but the descent from there is guesswork.