> so I assume the only thing I'm actually changing is the glass, and the rest of the assembly stays on the car. Is this correct?

I would expect at least new glass and new reflectors. They work together to form the beam pattern.

Just putting new glass on the headlights? Hmm.. Don't really see how that would change the light pattern from DOT to ECE, but please do tell if it does.. Would be very interesting.

The change should be pretty obvious if you park the car near a wall. The orginal DOT pattern usually has 2 bright 'blobs' in the middle which taper down to the sides and not much of a difference in light intensity between top and bottom.

The ECE pattern will show a very sharp dark/light horizontal pattern (hardly any light above the line) and a light 'flare' running up to the right at about a 15 degree angle (this illuminates the sidewalk and roadsigns).

Bye, Arno.