Those are very poor numbers for having new rings. (I wonder why they are no longer open???) Unless it still needed a valve job after the rings were done, all the cylinders should be in the 350-450+ range. The cylinder head was off and they were doing so much work to it already, a valve job should have been done at the same time.

With only 50k miles, there should be no reason for the head to leak if the job was done right. Mabye they didn't re-torque the head after it was run to operating temp???