Breaking in new motors

I'm putting in a reconditioned motor and I've been reading about breaking in periods. One method says to drive the heck out of it to set the rings and the other says to take it easy. Any thoughts?

The one time I had a new motor I took it easy, only 50 mph max for the first 2000 miles.

Change the oil after 500-1000 miles, use normal motor oil, and don't overheat it.

A popular notion is to accelerate and decelarate lots in the first 20 miles and then change the oil to get the metal fragments out. It talks like you need to put lots of load on the cylinders to seat the rings, but it's also important to do it in short bursts so you don't overheat the motor. Use normal oil for the first 1000 miles and then you can switch to synthethic if you want.