the exhaust port shape is slightly different between the 96-98 heads and the 99-01 heads. i think the exhaust ports on the
fr-500 heads are the same size and shape as the 99-01 heads. also, the 03 exhaust ports are similar in shape to 99-01 exhausts ports, except they are larger in size. aftermarket headers will interchange between the 96-98 and 99-01 heads. but, the headers/manifolds for the 96-98 4v's have provisions for secondery air injection on the number 1 and number 5 cylinders. the 99 and up headers/manifolds don't have secondary air injection provisions. if you use 96-98 4v aftermarket headers on 99-01 4v heads, all you need to do is block off the provisions for the secondary air injection on the headers. even though the port shapes are slightly different between the 96-98 and 99-01 heads, the exhaust flange openings on the aftermarket headers are bigger than the exhaust port openings on the heads, so you should not have any exhaust flow restrictions.
i would buy the FRPP headers before i would buy the JBA headers. Watson Engineering is the company that actually builds the FRPP headers. i personally do not like the quality of the JBA headers. i do not know how well the JBA headers fit but, i know the FRPP headers fit great. the FRPP headers are made out of stainless steel. the JBA headers are made out of mild steel. in my opinion, the FRPP headers are a better quality header and they are less expensive than the JBA headers. i did some touch up work on my FRPP headers but, the JBA also could use the same type of touch up work if you are trying to get that last little bit of power out of a set of shorty headers.
as far as long tube headers are concerned, i like the quality and fit of the kooks headers. the kooks headers are available in mild steel or stainless steel.
Did you get a 99+ or the FR500 intake (Are they out yet?)? If so, and you don't mind my asking, how much did the intake set you back? You do have to change don't you or am I suffering from brain damage?
I had wanted to do the FR500 heads, but the matching intake wasn't available when I had my engine done and Ford couldn't even tell me what I would need to order or how much it would cost me for a 99+ intake. Something astronomical I'm sure!
Hmmm. If I were to do this though, could I use my current valve train? Everything but the cams are all brand new. Chains tensioners, custom springs, Ti retainers valves, Stage 1 porting. The works. I would hate to buy all that stuff again. Pisses me off that I kept calling FRPP to find out when the intake kit would be released and they "couldn't tell me".
Would it even really be worth it? What kind of power gains would be had?