Sam, they are the same pattern so gen 1 and 2 3s items will fit. However, depending on what vehicle the 5s is in they might foul on the crossmember as they are shaped slightly different, well at least the ones i have come across are.
Factory gen2 3sge headers will fit and may be a slight upgrade over the 5s ones if you want on the cheap. AS for off-the shelf, hurricane, pacemaker, genie etc all make them. About $450 mark from memory
Check Ozcelica maybe?
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