Test it. It will tell you what it wants. Start at 36 like suggested, and try 2 less, 2 more, and then look at mph. It will tell you what it wants. I would also lock the time out.
There is no "set" number for any engine, like a sbc likes 36, or a BBC likes 38, or 18 degree heads want 28 tops, etc etc. The engine will tell you what it wants. Listen to it, do not try to tell it what it wants. That doesn;t make the most power
Frank