2002 Allroad headlights ona A6 sedan
 

Anyone know if the Allroad headlights will fit a C5 sedan?

2002 Allroad : 2002 C5 A6

It depends on which engine! 4.2 no 3.0 probably.

V6 cars.

Next crazy question, are the headlights physically different as far as mounting and body fit, or is it just the way they look. (Reflector/lenses style)?

allroad headlights regardless of year are pre-facelift and will only fit other narrow-body models through 2001. They will not fit 2002 and later narrow-body models.