99 range and 52 prayer. Also, it's optional, but in my experience zerkers are usually better with 75-80 atk. Barrows gloves would definitely be useful too.
60 attack is nice though, getting any higher is generally a waste. Unless you plan on getting 80 dung. The lower you can keep your cb as a zerker, the better.
Even with chaotic, the cb levels are hardly worth it.
Now adays, 52 prayer is obviously nice in pk.
Turmoil zerkers thrive immensely at 60 attack.
Stick around 90 cb, with insane attack power.
But anyways.. If you don't have b gloves at 45 def, it's pretty crappy.