What to do with new motor?

You can check for leaks before starting the motor. I filled my 360 through the thermostat hole in the intake before I put the thermostat in. It's a good thing I did because I forgot the small bolt that is behind the outlet on the waterpump. Talk about a last minute pain in the ***.

mullinax95 is right, 20 mins at 2200rpm on a virgin motor gets pretty hot. Paint, gaskets, and sealer all start to cook, smoke and smell really weird. Antifreeze also acts as a lubricant for your waterpump.