The flanges on the auction headers have a few problems with them. While the ends are fairly close, the flanges on Kustom built headers, as well the other manufactures that built for Chevrolet, used a “cut-out” flange design, not simply notched as the action headers are. Please refer to the article on Rob Starks Cross Ram off the "Prestige Page" below:http://www.guinns-engineering.com/Documented%20Components.htm
In addition, the pipes appear to be only Mandrel bent, where as the second design (PN #3916383-84) Z/28 headers had a few spots that were partially cut, reformed and Heli-Arched. Also note the collector style is incorrect and length of the primary and collector tubing is off.
Unfortunately, I have not finished the Ricks Factory Header article on the "Prestige Page" that goes quite deeply into the topic. Please stay tuned and check back to the page frequently for updates to information related to the HD options
Regards - Wayne