69 Dart Exhaust

Can I assume that regardless of what header I use the H or X pipe will always line up with them?

No, I would not assume that. If you have an X or H pipe hooked up to a set of Hooker headers, I would not expect them to be a direct bolt-on if you switch to TTI's. TTI's X-pipe will fit TTI's headers. Anything else, I would expect needs to be modified to fit.