Try Stainless Headers Mfg. - they build for various replicas / kit cars, but they also have a "unique header fixturing device makes it possible to get perfect header to side pipe alignment for your cobra without having the car at our location. Once put into place, just tighten the locking bolts. Our craftsmen will reproduce your exact configuration."
Video:
https://youtu.be/go9raemoXDk
Cobra Kit Car Headers - Stainless Headers Mfg., Inc.