Ideal amount of oil for a /6

Mobil suggests that Mobil1 can be used for break-in:
http://www.mobiloil.com/USA-English/MotorOil/Synthetics/Myths.aspx

I'm not sure if the break-in for a new engine is the same as rebuilt engine but your success with break-ins with synthetics seems to confirm Mobil's suggestion. It probably wouldn't make any difference if you used a high quality conventional oil for the first fill and switched to synthetic afterward.