Do I need to clean the mounting surfaces before installing this gasket?

Yes. Scrape away old gasket material and carbon buildup from both the header flange and manifold surface. A clean, flat surface ensures a tight seal and prevents the new gasket from blowing out under heat.

What hardware do I need to bolt the header back on?

Hardware not included with this gasket. You'll use the existing studs or bolts already on your vehicle — test-fit to confirm they're clean and not stripped before reassembly.

Can I reuse the old bolts, or should I replace them?

Inspect your existing fasteners first. If they're clean and threads are solid, they'll work fine. If you see corrosion or damage, new studs or bolts are cheap insurance against another leak down the road.