Dynatrac is the most "custom" kit... and the most expensive... the spindle is a custom machined piece.
The EMS Offroad kit uses an off-the-shelf spindle (Ford??) that is redrilled... and from what I have read, the holes are sometimes very close to existing holes. But it is a lot less expensive, and they seem to work just fine.
I have the DT kit, but EMS wasn't an option at the time...