Do I need gaskets or clamps to install this?

The assembly mounts at factory points, but gasket type and fasteners aren't specified in the product data. Have gasket material and hardware on hand before you start—check your service manual for the exact spec.

Can I reuse the old bolts, or do I need new ones?

Always use new fasteners when installing exhaust components. Old bolts can seize or fail under heat cycles. Pick up a fresh set rated for exhaust heat before you pull the old converter.

Do I need to do anything to the old manifold before installing this?

Clean the mounting surface on the manifold to remove carbon buildup and old gasket material. A scraper and wire brush will do the job—you want a clean, flat seating surface for the new gasket.