As far as the exhaust - what shape are your manifolds in?
If you are replacing everything, I think the consensus is that the Banks system is about at the top of the pile. Not to discount other midline (and more affordable) header systems, though.
As far as the header back, I think I would go with a custom shop. Probably a little cheaper, and you could go with a larger diameter and better grade of pipe at the same time.
With all modifications, keep in mind the goal to let the 454 breath better and get rid of the heat.
As far as the fridge, do a search on the forum threads. Several sites on the web also offer excellent troubleshooting procedures, and I have found replacement boards from Dinosaur to be quite affordable. I was able to redo both of my fridge boards for a couple of hundred bucks.
Good luck, keep the forum advised of your progress!
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