Clevelands in Mavericks have the same header maladies as Mopars. 1K bucks is the starting point. Torinos and Rancheros have headers starting out at 150 bucks.
Clevelands in Mavericks don't need aftermarket headers. I came as close to dying in the one I put together as I ever got. With 2.88 gears it buried the speedo in second.