I have had dealings with FPA but not a FE. I asked them to make me a set of long tube headers for my 351W in 65 coupe with RRS rack and RHS heads. Spoke to Stan Johnson over the phone, he has some bad reviews but they were really great for me. Headers arrived on time and cost a bit less than half what a custom set cost here. Fit is almost perfect for never seeing the car with the rack. Just had to bash a small section at one of the plugs and that was it.
I do believe they know FE's very well so might be worth a phonecall.