Dougs headers idiot tech support
If you do spend another $100 on tti's... guess what... you'll be modifying your z-bar. I've had 5 or 6 4 speed a body cars with these headers and all of them needed z bar mods with both brands.
Unfortunately the tech support at these places is lacking most of the time. I know that the dougs catalog says those 453 headers don't fit 73+ cars or cars with 727's... both are false. they fit fine with either and both!
tti's are a copy of the dougs with some changes in routing the step set up.
tti will tell you to bend the z bar... they acted like they never heard about it either when I spoke with them about the issue. Mayeb they've changed their instructions.