What kind of diode should I use across the load?
Thanks to a comment on the question, I found the answer in a separate document associated with the device. Lesson learned, don't assume all the documentation is in the data sheet.

The VN2070AJ is


  designed  to  successfully  pass  the  1,  2,  3a,  3b  and  4 
  ISO-7637  standard pulses test - simulating the low energy voltage
  spikes. These values must be added to the voltage battery (for cars
  about 13.5V) to obtain the actual voltage. The N.5  ISO7637  pulse 
  simulates  the  alternator  load  dump  in  the  case  of  a 
  Generator  with  an  internal impedance of 2Ω and different values of
  magnetic field of the excitation circuit (see figure 8 for the level
  IV pulse); this occurs when the battery is disconnected whilst being
  charged by the alternator. The voltage spike  can  reach  duration  of
  approximately  ½  second  and  it  is  of  high-energy  nature 
  because  of  the alternator's low source impedance. Where a
  centralized clamp circuit is not provided or ISO7637 rated devices are
  not used, an external zener Dld diode is necessary to clamp the
  transient voltage battery.


Therefore, Dld is a Zener diode.