A regular magnaflow cat is under $100. Don’t gut your cat, it pointless. Just replace it with a weld on magnaflow if it is compliant. If not then get a replacement on rock auto. A gutted or removed cat is not an improvement over a good working unit. Just lookup how they work. They simple and effective devices. Essentially they are an afterburner for anything that didn’t get completely burned off in your engine. They aren’t a restriction or a filter. Here is a list of some: https://www.summitracing.com/dom/search/brand/magnaflow/part-type/catalytic-converters?SortBy=Default&SortOrder=Ascending
They are available in both stainless and ceramic elements with or without heat shields (with is much better for our trucks)