[GMCPaul]

The reason you are having such a hard time find clear sidemarkers and clear taillights is its illegal for retailers to sell them as the federal goverments agency NHSTA " National Highway Traffic Safety Administration "
because NHTSA has also stepped up enforcement against restyled combination lamps that are missing required functions existing on the original-equipment lamps. This would include replacement front- or rear-combination lighting equipment that do not have a required reflector, amber or red light, “DOT” marking or mismarked wattage.
The sidemarker when not lit must reflect Amber in the front and reflect red in the rear, the same holds true for the clear taillight lens it must reflect red when not lit, so the 73up truck lenses with clear outer shells and red lenses over bulb area reflect red when unlit, but the 67-72 clear taillight lenses do not have a red reflective lense over bulb area so they will not reflect red when unlit and the same holds true for the sidemarker lights, parking lights can still be sold clear because they are not required to reflect amber when unlit, only that they emit a amber light when lit.

And we can't use the disclaimer For Off Road use only because the NHTSA says

The NHTSA has also determined that a commonly used disclaimer “for off-road use only” has no legal meaning and is not recognized by the agency as the manufacturer, importer and retailer are not in a position to control use once a product has been sold. Any equipment offered for sale which is covered by FMVSS No. 108 (headlamps, taillamps, side markers, etc.) must comply with the standard.

and if we as retailers do not follow these guidelines then we are violating Federal Guidelines and can be fined the same amount as the manufacturer and importers for selling them and these fines begin in the 5 figure range and can go as high as 6 figures.

The NHTSA is also pushing all states to begin enforcement at the local level and if not implemented they plan on cutting funding to the states through legislation.

this also applies to HID Headlight conversions that exceed the legal wattage on headlights, in one investigation, the NHTSA found an HID conversion headlamp exceeded the maximum allowable candlepower by over 810%.

Under FMVSS No. 108’s Section S7.7 (replaceable light sources), each replaceable light source for headlamps must be designed to conform to the dimensions and electrical specifications for the headlamp source it is intended to replace. Example, if an HID kit is marketed as replacing an H1 light source, then it must match the H1’s wire coil filament size and location, the electrical connector size and location and the ballast design for use with an H1 light source (which is impossible since there is no ballast). Consequently, companies that are manufacturing HID light sources (e.g., D1S, D1R, D2S, D2R, 9500, etc…) with incandescent light source bases (e.g., H1, H3, H7, H8, H9, H11, H13, HB1, HB2, HB3, HB4, HB5, etc…) should be aware that this light source design would not be one that conforms to FMVSS No. 108, and could not be imported and sold in the United States without violating Federal law.

GMCPaul