Cam And Lifter Hardness Testing

[1] Roller cam is flat, although the rollers are often crowned. I believe the crowning is done to [a] help tracking [ b] the roller 'flattens' out under load for more even load distribution.
[2] The 440 6 pack low taper cam/lifters was to reduce wear with the stronger valve springs.
[3] Low taper provides more contact area, so less wear.