I'm not sure coating will help with weak welds but may help with hot spots in the metal that could crack. It's a gamble. You'll need exhaust manifold gaskets but shouldn't need head gaskets that you asked about earlier, new exhaust bolts wouldn't hurt, be sure to use anti-seize .
Those heperformance headers look like they would get in the way of your A/C evap box. Does anyone know if the OBX headers allow you to keep the factory air?
1999 ExRanger 2wd XLT 5.0, Explorer V8 and transmission swap, 3" straight pipe exhaust with single muffler, explorer roof rack, 2006 mirrors, cut front 60/40 seat to buckets, 4 in lift spindles up front and shackles in back, more to come.