Do I need new bolts to install this gasket?

Your existing header bolts will work, but check them for corrosion or damage before reinstalling. If they're heavily rusted or stripped, grab fresh fasteners while you have the header off.

Should I clean the header and manifold surfaces before installation?

Yes. Wire brush or scrape both mating surfaces to remove old gasket material and carbon buildup. A clean seat ensures the new gasket seals properly and prevents exhaust leaks.

Can I reuse the old header bolts if they look okay?

Inspect them closely — exhaust bolts see high heat and vibration. If threads are intact and bolts aren't corroded, they're reusable. When you torque them back down, tighten evenly in a cross pattern to avoid warping the gasket.