Will these bolt straight to the stock manifold location?

These are designed as direct replacements for the factory manifolds. Test-fit before final fastening to confirm alignment at all mounting points.

Do I need new gaskets and hardware to install these?

Header gaskets and bolts are sold separately. Grab a fresh gasket set and stainless hardware rated for header temperatures — reusing old gaskets causes leaks.

Can I run these with a stock exhaust system, or do I need a cat-back too?

Headers alone will work with stock piping, but you'll see better flow and performance if you upgrade the cat-back as a follow-up. The header improvement isn't bottlenecked by factory downstream components in stock form.