Well, I'm embarrassed to have to tell you guys this, but I figured out my problem today.
The collector was, in fact, hitting the torsion bar. The reason, however, was because the #1 cylinder primary was hitting the motor mount clamshell.
I ended up 're-engineering' the pipe with a hammer about 1/8" and now it fits fine.
I'm still not impressed with how unnecessarily tight the clearances of the header are in a few spots, or the way the included pipes are routed, but at least I can get back on the road.
Thanks again for all of your help, anyways. I probably would have just lit the truck on fire, had I not had somewhere to vent my frustration.