Header Questions for a 73Duster

I read in the second post they use both of the terms "chassis" and "fenderwell".
but one part#?

I've had the low hanging headers and swore to myself I'll drive it easy so they will be ok. The next thing I know is I'm 30 mph in traffic and cross an intersection with a little dip and BAM 2 flat tubes.
For a street car I'll spend the extra for the tight to body ones cause I'd be spending the money buyin another set later anyway. :angry7:Not to mention doin the work again.