Maybe it's just that the guys I know are pretty casual about the whole running in process, but they've always just used something like Castrol R.
I've also heard that
synthetic isn't a good option for running in.
About your camshaft - is it a roller or flat tappet?
If roller - I wouldn't ever use
synthetic
If FT - depending on your spring pressures, I'd consider taking the valvesprings apart and running in the motor just with the inners.