The key is usable power. You wont make peak power with That 847 until 6k plus. Even a refreshed stock bottom end won't like being turned that high for to long. I think my cam was overkill for stock heads. I was making peak power at 5900-6000. After that the power descended pretty rapidly. I also believe a custom grind will give you the best of both worlds. If you want screaming top end buy the biggest cam offered and shift it high on borrowed time. If you want a noticeable difference good low mid and top end go with a cam that's custom ground too fit your needs.

 

Dennis thanks for the info def something I'm gonna check into