REGARDING YOUR HEADERS.
When my engine was redone the builders wanted to use 22/4 inch headers pipes to the mufflers. We built a beautiful set of headers that instead of going down and through the rear suspension like the original went up.
The tubes come off the heads and go up and back to a collector, over the top link of the hub carrier and then turn straight down, they turn again to the back of the car and straight in to the mufflers. It works great as there is no exhaust heat near the starter or motor mounts.
The gave me the large header pipe and no interference with the rear suspension. My headers are equal length tubes and very efficient. I have never had any trouble with them, they are jet coated silver.