In regards to headlamp reflectors:
On the front at the same height, with an equal number at each side of the vertical center line as far apart as practicable
http://www.fmcsa.dot.gov/rules-regulations/administration/fmcsr/fmcsrruletext.aspx?reg=393.11
(this linkie is for commercial vehicles, but it's the same for private, I just cant find that linkie right now ... need coffee )
On the front at the same height, with an equal number at each side of the vertical center line as far apart as practicable
http://www.fmcsa.dot.gov/rules-regulations/administration/fmcsr/fmcsrruletext.aspx?reg=393.11
(this linkie is for commercial vehicles, but it's the same for private, I just cant find that linkie right now ... need coffee )