I picked Kooks headers for my engine rebuild to get the 3" bolt spacing (versus 2" spacing for typical headers), eliminating a pinch point, and improving exhaust flow through the heads, and my heart went pitter patter with the thoughts. Then after waiting several weeks (months) they arrive and look oh so gorgeous, though they do come in 3 pieces per side. I trial fit them on the engine on the stand, and they still look gorgeous, but they don't clear the Moroso 7 quart pan. Fortunately a few taps from a sledge fixed that, so no big deal. Then I try to install the headers in my 89 Mustang, and they don't clear my aftermarket K member. Kooks claim they clear factory and AJE K members, and might clear UPR. So after much research, I order an AJE K member, pay for it, wait for it, and then install it. Headers clear and I think I'm home, it's a sweet day (though I'm not fond of the AJE K member). Then I find out the AJE moved the steering rack, and now my steering shaft is over an inch short, which costs me another week and custom work to resolve. I also slowly discover you really need to assemble the three piece headers in a precise order, or they don't go together very well. Next, the Kooks headers don't allow the exhaust to clear the Ford transmission mount, nor do they connect to any standard H or X pipes. More custom work to modify (lengthen) the transmission mount and fabricate an exhaust system, since no muffler shop will touch the car without cats. I sure hope the dyno shows they are worth all the trouble they've been. Every other engine I've rebuilt has taken a few days to reassemble the car, but with these issues, it has been weeks....but they do look sweet....