About3 yrs ago I coated the inside of my exhaust pipes (they were new) with POR-15. I soaked a sponge with the paint and pulled it through the pipes with a long wire. Went twice in both directions. I don't have any rust through evidence at all. This was a procedure recommended by the POR literature. I don't know if they still recommend it, but it worked for me. Sorry I don't have any experience with the rest.
72 El Camino
Kent; if you're still running the original cast-iron manifolds, Eastwood has what you need. If you're running tube headers, I would have them coated by someone like Airborn or HPC.
For pipes my choice is aluminized. In my opinion it is better than stainless and a lot less expensive. I have had aluminized on my 70SS for 10 years now (it is driven every nice weekend) and it still looks great.
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