The way I understand it the high ZDDP is a requirement for the break in cycle of a new cam and new flat tappet lifters. After break in it is not so important. If you used a new or reground cam and new or resurfaced lifters in your rebuild you should definitely use a high ZDDP break in oil.
I still use a supplement with every change on my classics with flat tappet cams just in case.
