Ho jeez. Well, ask yourself first why you're getting cams. Getting a stage two cam or "biggest cams i can put in my 4.6" with NPI heads and intake manifold is at the least illogical.
Look into comp cam xe268H's for you NPI heads and consider a pi intake manifold!
If PI heads and intake then cams make more sense considering the gains from cams are up top in the rpms where air flow restriction hurts the hardest.
Then look into xe262ah's or CMS stage 1's. If you're bold and you will degree the cams perfect, CMS stage 2's (XE270ah's may not have enough piston clearance). Even then a ported PI head makes sence.
Are you doing it for the sound?