If you match brands for sure they will fit. If you want to get the best of each part and the brands are different, it is not that big
of a deal to adapt them. My car came with Mac and it is good,
others may disagree. Get what you like sound,performance etc.
You can get three bolt collector/reducer (any sizes you need) which can fit any long tube headers to the exhaust pipes. Summit carries two kinds - weld-on or slip fit (using clamps).