FPA's headers are top notch... and so is Stan! He worked with me on a set for my '72. Same header as the '67-'73 Mustang/351W. Couldn't fit more perfectly, even with the C6! Stan told me of any possible interferences that could have popped up during install and how to remedy it... ahead of time. The ball and socket collector definitely was the way to go, too. Just be sure he knows exactly which head you're using, and what size exhaust you want to run from the collector on back.
All in all, a great product and some of the best money I've spent. Period!
Kevin