I was in the same boat as you, couldn't find any off the shelf headers that fit 4x4 OBS ls swap trucks, came across this video after someone pointed me towards Fast2dr on youtube. he has a set of pacesetter longtubes on his 5.3 swapped 2dr hoe, p/n: 70-2265. they appear to fit nbs 99-07 4wd trucks

here is the video:
https://www.youtube.com/watch?v=fZ_0...ZVfwh0&index=8