First, anyone saying that you need to flush to switch to synthetic is about 30 years out of date. There used to be an issue back in the 70s, but not anymore.
Second, you don't have to worry about protecting a flat tappet cam, because you don't have one, it's hydraulic roller. I'm not going to get into the whole ZDDP debate. One side says the high ZDDP levels were really only useful as an anti-oxidant with modern engines, others say that's it's better for engine protection. I've never seen any hard data, so the only answers you'll probably get are going to be opinions.
