I didn't have any cats to keep. The truck had none, my truck has none, the monte carlo had none, and the camaro did have one but it was smashed. I had to buy them because of inspection here, visual to make sure you have a cat, that's it. So on the truck and monte I had them gut the old cats, they save old ones bust the guts out and weld em on. Both them ran headers and no other emissions so no need for cats. Other then looks to pass the inspection.
There is a place online that sells them now for the same price, and stainless ones for $5 more. They aint busted out, solid pipe all the way thru but looks like a cat on the outside.