I cant for sure answer all your questions about your truck, but I would for sure check to see if it's legal in your area to run without cats... some areas of the country let you get away with it, but you will want to be sure in order to avoid any possible fines...
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Also if you dont want to replace both cats, you can just replace 1 and have bill write you a tune to match.
I know there are places that sell manifolds, cats, and cat-back exhausts online, but IMHO I think that you might want to go to an exhaust place and see what they think, and see how much they charge.
Hope I helped
