Do I need to clean or prep the cylinder head surface before installation?

Yes. Scrape away any old gasket material and carbon buildup from both the header flange and cylinder head. A clean, dry surface ensures a tight seal and prevents leaks.

Will this gasket work with an aftermarket header, or only OEM?

This gasket is designed for the factory header bolt pattern. If you're running an aftermarket header, check its flange hole spacing and diameter first—different headers may require a different gasket.

What hardware comes with this gasket?

Only the gasket. You'll use your existing header bolts to clamp it in place. Inspect those bolts when you remove the old gasket—if they're stripped or corroded, replace them before reinstalling.