TJ, if you have a BIG fan or two, set them in front and give it a little help. Lets see if this is a simple airflow issue. If it will cool down with airflow, some shrouding and higher CFM fan/fans will help with the low speed/idle driving. The radiator I have isn't high capacity by any means. There is very little room. Probably just enough capacity to dissipate the heat from a 60HP motor! I didn't think the one you ended up with was much larger. I don't think they hold much water.

Try more air. If it will cool down then you know its not just running away. 225 is hot enough. I would keep adding air to keep it under 220. It is a new motor. They might run a little warmer for a few minutes but, I wouldn't expect it to run but a few degrees warmer while the rings break in. That should be well on its way from the dyno. It should be fairly broke in.