They are what is called "tufftried" (sp). It is a chemical pickeling process. It only hardens the crank a few ten thousands of an inch (.000x) deep. Once the crank is "cut" the tufftriding is gone. There were very few shops "back in the day" that could do it. Now I know of none. I have a 170 slant six crank that is standard size, and hard chrome plated so I could run a hard bearing without scoring the crank or pounding out the bearing. The crank was done by Lunati in the mid '70's, and I used a tri metal bearing instead of Babbitt.