TTI headers

I'm installing a 408 stroker in place of my 318 factory motor. I have been told the TTI headers are the only ones that will fit out of the box. I have an 833 4speed for a tranny. Will these work and do I need the zbar mod.part from them as well? Any others work that are cheaper?? Do I place them in the car before I install the engine?:blob:
Thx