break-in oil?

I'm getting ready to do a new 273 with a flat cam also. I have been using Royal Purple for my Harley and cars for several years since I blew a Harley on Mobil 1 and they wouldn't stand by their product. Wanting to make sure I was on the right track, I e-mailed Royal Purple and they told me to use their break in oil and after that to use either their 10W40 or 15W40 as they still have high levels of zinc.
According to the e-mail, there was no reason to use more zinc additive.
I bought a case of 12 on line for about $90.00 delivered. There are instructions right on the bottle.