Here are a few photos of the Group 4 Pantera that Quella’s son was building in Castle Rock when I was last there. I did not take as many photos of the car as I thought, but hopefully these will give you some more ideas for your 180’s. I do not know who builds the actual 180 headers for Quella’s cars, but I don’t believe they build them in house.
The car was still a long ways from being finished but already looked great. The Group 4 conversion was all steel. On the 180’s, I particularly liked the rear support that Quella had fabricated for the mufflers. Quella’s son also mentioned that the muffler exits would have rings around them when he was finished fabricating the muffler system, etc.
I hope this helps and please keep us posted on your build.