When installing headers you will need header bolts, factory exhaust manifold bolts won't work. These Mr. Gasket Header Bolts are Grade 5 for strength and black oxide coated. If you've ever had a set of headers where a socket just seemed it wouldn't fit these might be your answer. These bolts also have a socket head or Allen key drive in the center for just that problem. Sold as a set of 12 Fits: AMC 290-401 Chevrolet Small Block 262-400 Chrysler Big Block 383-440 (Does not Fit 426 Hemi) Pontiac 326-455 Oldsmobile 330-455