OK, it's after midnight and I give up, but here is what I have found which is basically what I already posted.
ELECTRONIC CODE OF FEDERAL REGULATIONS
[TABLE="width: 90%"]
[TR]
[TD]
e-CFR Data is current as of March 6, 2014
[/TD]
[/TR]
[/TABLE]
Browse Previous | Browse Next
Title 49: Transportation
PART 571—FEDERAL MOTOR VEHICLE SAFETY STANDARDS
Subpart B—Federal Motor Vehicle Safety Standards
§571.108 Standard No. 108; Lamps, reflective devices, and associated equipment.
Table I-a—Required Lamps and Reflective Devices
[TABLE="class: gpotbl_table, width: 100%"]
[TR]
[TD="class: gpotbl_cell, colspan: 5, align: center"]
Additional Lamps Required on All Multipurpose Passenger Vehicles (MPV), Trucks, and Buses, 2032 MM or More in Overall Width[/TD]
[/TR]
[TR]
[TD="class: gpotbl_cell, align: left"]Clearance lamps[/TD]
[TD="class: gpotbl_cell, align: left"]2 Amber[/TD]
[TD="class: gpotbl_cell, align: left"]On the front to indicate the overall width of the vehicle, or width of cab on truck tractor, at the same height, symmetrically about the vertical centerline
May be located at a location other than the front if necessary to indicate the overall width of the vehicle, or for protection from damage during normal operation of the vehicle.[/TD]
[TD="class: gpotbl_cell, align: left"]As near the top as practicable[/TD]
[TD="class: gpotbl_cell, align: left"]Steady burning.[/TD]
[/TR]
[TR]
[TD="class: gpotbl_cell, align: left"][/TD]
[TD="class: gpotbl_cell, align: left"]2 Red
(not required on truck tractor)[/TD]
[TD="class: gpotbl_cell, align: left"]On the rear to indicate the overall width of the vehicle, at the same height, symmetrically about the vertical centerline
May be located at a location other than the rear if necessary to indicate the overall width of the vehicle, or for protection from damage during normal operation of the vehicle.[/TD]
[TD="class: gpotbl_cell, align: left"]As near the top as practicable, except where the rear identification lamps are mounted at the extreme height of the vehicle.
Practicability of locating lamps on the vehicle header is presumed when the header extends at least 25 mm (1 inch) above the rear doors.[/TD]
[TD="class: gpotbl_cell, align: left"]Steady burning.[/TD]
[/TR]
[TR]
[TD="class: gpotbl_cell, align: left"]Identification lamps[/TD]
[TD="class: gpotbl_cell, align: left"]3 Amber[/TD]
[TD="class: gpotbl_cell, align: left"]On the front, at the same height, as close as practicable to the vertical centerline, with lamp centers spaced not less than 6 inches or more than 12 inches apart[/TD]
[TD="class: gpotbl_cell, align: left"]As near the top of the vehicle or top of the cab as practicable[/TD]
[TD="class: gpotbl_cell, align: left"]Steady burning.[/TD]
[/TR]
[TR]
[TD="class: gpotbl_cell, align: left"][/TD]
[TD="class: gpotbl_cell, align: left"]3 Red (not required on truck tractor)[/TD]
[TD="class: gpotbl_cell, align: left"]On the rear, at the same height, as close as practicable to the vertical centerline, with lamp centers spaced not less than 6 inches or more than 12 inches apart[/TD]
[TD="class: gpotbl_cell, align: left"]As near the top as practicable
Practicability of locating lamps on the vehicle header is presumed when the header extends at least 25 mm (1 inch) above the rear doors.[/TD]
[TD="class: gpotbl_cell, align: left"]Steady burning.[/TD]
[/TR]
[/TABLE]
http://www.ecfr.gov/cgi-bin/text-id...e9e9e026935&node=49:6.1.2.3.37.2.7.8&rgn=div8
This is a very long document, but this chart is about mid screen when you scroll down.
Right above this section it talks about headlights, brake lights, etc, so the way I interpret this is: clearance and identification (three in the middle) lights are required for vehicles > 80" wide just like headlights, brake lights, etc. So, if you elect to remove them you're in violation just like you would be if you removed the headlights or brake lights.
This Standard is about as official as it gets, so I don't think we're going to find anything to the contrary.
I hope this helps and I know I learned a few things researching this.
~Pat