For what its worth you can create alot of space by not only moving the engine around alitle but also by shimming the driverside mount up to move the passanger side header away from the torsonbar,these cars are terrible in tollerances and sometimes everything just falls into place once you take out all the stock screwups,sometimes its not possible,but you never contacted Dougs to see if they could help you incase you just got a bad passangerside header,crap like that happens in manufacturing and some but sadly fram from all manufactures will do the right thing.
Sad that you never saw the isue with the Z-bar ahead of time im sure i have seen it mentioned alot of times over the years, i wonder if its the result of Dougs getting their hands on some oddball car when making the first headers and then nobody told them about the problem? Dougs is one of those companys that seemed like they did care about making things work...
Headers often are a pain,but thats what happens when you try to fit 4 pipes in a space only designed for one in the first place..