The 03+ have larger exhaust ports but it doesnt seem to make much of a difference. The FR500's are the absolute best of the 4.6 heads and will work very well, especially in ported form.
The FR500s have almost the same intake port as the 03/04 and an exhaust port identical to the 99/01 head. The 99/01 heads work great with FI so the FRs should be even better.
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