Installed on a '68 Plymouth 225 Slant-6 engine. The product is nicely cast with a machined gasket mating surface. Bolt holes lined up perfectly and were sized correctly for the factory bolts. A quality part - highly recommended, and made in the USA. TIP: Make sure the head mating area is clean and smooth, use copper spray on both sides of your gasket for better sealing - the stick will also hold the thermostat in position as the housing is aligned, if your stat has a notch or hole in its ring - position it straight up. Don't forget to use anti-seize on the bolts, and use washers to prevent galling and creating stress-risers on the casting. Torque to 20# incrementally (10,15, 20).