Factory Cab Lights

[Uncle G]

I have an 85 C20 Scottsdale. The vin says its a HD ( M in the vin). It came factory without cab lights. What trucks came with factory cab lights? I'm having trouble finding this info. Can somebody put me on the right trail? Not sure if this is the right place to post this cause I'm new.
Thanks

[Jason S]

Are you referring to the roof mounted clearance lights? 

They were an option on most C-10 & C-20 cab styles and generally standard on C-30 1-ton dually trucks and heavier.

[zieg85]

Here is an option for you.  They offer several style light bulbs from factory style 194 bulbs to bright LED  https://www.ebay.com/itm/5-Amber-Lens-Cab-Clearance-Light-Marker-1313A-3020-2825-White-LED-for-73-87-GMC/122652764481?hash=item1c8eaca941:g:mU4AAOSwl~tZlTg6&vxp=mtr

[Uncle G]

thank yall

[zieg85]

FWIW the M in the VIN signifies a 5.7L engine

[Uncle G]

Thanks zieg85
I looked at one of the decoders and it showed a vin with L as 350 and M as 350 HD. I think chevy made a light duty 3/4 ton and I was told that they didn’t come with cab lights. I was talking with another chevy fan and he said that back in the 80’s you could order trucks with cab lights. After talking to him I believe only 1 ton trucks came factory with cab lights. All others had to be ordered. Does that sound right?
Thanks

[zieg85]

Sounds about right.  I had an 84 Cab and Chassis that had them and a 87 that didn't.  I had a 87 Crew cab dually that did.

[75gmck25]

If you are talking about the lights on the top of the cab, those are clearance lights.  The lights are mandatory for a dually because the truck is more than 80" wide.  They are also required for most 1 tons because of the GVW/height/length/trailer towing (the DOT regs are a little complicated, but it boils down to needing lights for tall, long vehicles and vehicles that pull big trailers). Some 3/4 tons may also  require the lights.

Bruce

[Jason S]

I looked at one of the decoders and it showed a vin with L as 350 and M as 350 HD.

The VIN code differences are about emissions equipment.

http://forum.73-87chevytrucks.com/smforum/index.php?topic=28056.msg233789#msg233789

[Uncle G]

I think I got the answer to my cab lights question (maybe??). I talked to a mechanic that worked for a Chevy dealer during the 80's and he said the 3/4 ton trucks that had cab lights were put on by the dealership. He said they didn't come from the factory with them.

[zieg85]

Clearance lights were standard on certain trucks, any dual wheel.  Pretty sure you could order them if you had your truck built.  I know I had them on my 92 I ordered and it was a 2 wheel drive 1/2 ton

[Stewart G Griffin]

Not totally positive on this, but if the GVWR is 8600 lbs or higher, then all 5 lights are required.   If the vehicle is wider than 72'', then you need the outer 2 clearance lights.

[Jason S]

Option Code U01 - Roof Marker Lamps

They were included when option R05 Dual Rear Wheels (DRW) was specified. Roof lights show as included equipment on later 1980's K-30 single rear wheel models.
 Their availability to California vehicles seems to have been rather restrictive. Otherwise, they were offered as a factory installed option that could be selected in the remaining 49 states. 

Depending upon the model year, the option may or may not have been available on C/K-10 vehicles. It also appears from various option lists that marker lamps could not be ordered for California emissions trucks unless they were DRW.

Additional information on the various options for 1985 are available from the link below:
https://www.gmheritagecenter.com/docs/gm-heritage-archive/vehicle-information-kits/Chevrolet-Trucks/1985-Chevrolet-Truck.pdf
Curiously, some of the 1985 information kit option list pages have a October 1985 date and shows for 1986 model year. 

Using the 1985 Chevrolet truck information kit (with October 1985 dated option page), shows roof marker lamps could be ordered if either NA-5 or NA-6 emissions was also selected on C/K-20 pickup trucks and Cab & Chassis Trucks (10-1985_OptionList & 1985_U01_option_Cab_Lights_pickup).

Additional examples, the U01 - Roof Marker Lamp option was available on 1975 models (1975 U01_option_Cab_Lights). The lamps were included on R05 DRW specified trucks. Also noted as "Not available for registration in the State of California." 
 
Suburbans could also be ordered with the U01 Roof Clearance Lamp option (1-1991_Suburban Options) though not to models with YF-5 California Emissions .

The 1981 Pickup option list shows the roof marker lamp was available for pickup models, no restrictions given other than it was unavailable if YF-5 California Emissions or Z77 Chevy Sport options were selected (1981_OptionList_Example).

By 1984, U01 Roof Marker Lamp option was limited to "C-K2-3 models only" and still unavailable to California Emissions optioned vehicles, unless R05 Dual Rear Wheels were specified (1984_U01_option_Cab_Lights).

[zieg85]

nice, I learned something today, thanks for sharing

[Uncle G]

Thank you for that Jason.