Headers are pretty straightforward to build. Just buy a bunch of 90 and 45 degree bends and piece them together.
Start with the most difficult pipe first and then build forward from there. I cut the bends and then tape the sections together with masking tape as I fit the pipes together. When you're happy with how they run you can tack them together and check again.
Checking the fit with the body on:
All finished bar the rear mounts and ceramic coating
You can buy most of the lazer cut flanges from a good exhaust shop.
Cheers