Dont fall into the trap of thinking something wont "hurt" -- anything used improperly can hurt... I would say that if you had to choose, to choose cams- but Id also port/polish the heads and intake as well, and definitely add the normal variety of bolt-ons such as headers, pullies, etc.
The reason I say go for cams is because you could always add N2O or a blower later, and the benefits would be much greater. Ive also heard of a few too many 'grenaded' 4.6 motors that used N2O.
My $.02
Steve
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