It would probably be cheaper to get a used box blade with the ripping shanks than making one with chisel shanks.
Have you looked at the land planes? They work well for leveling driveways. As a matter of fact, that is what they use to maintain the gravel portion of the road that reaches Pike's Peak.
The land planes can have angled blades to help build the crown in you driveway or have the blades straight across for generalized leveling. Either one can be use to maintain your driveway. If you build one, the cutting edge is normally 3/4-1" below the side skids.
There are several threads here on homemade ones. Also check out YouTube for videos.