Originally Posted by Brad Allen
Here is a picture of the factory lights from 1951. Also a complete NOS set, I believe they are 4"?

Close but, no cigar this time Brad .

No such thing as a GM truck Guide 4" lamp but, the dealerships were known to install the INCORRECT
Guide 4 5/8 inch {2013-A} and the 5 3/4 inch {2002-E} on some A.D. trucks.

In all actuality, the correct accessory lamps for the 1951 trucks is the Guide 5 inch {2025-A } lamps.
GM part # 986524 Group # 9.774.

http://pic20.picturetrail.com/VOL1568/13678754/24528751/409107283.jpg

http://pic20.picturetrail.com/VOL1568/13678754/24528751/409107284.jpg

http://pic20.picturetrail.com/VOL1568/13678754/24528751/409107297.jpg

http://pic20.picturetrail.com/VOL1568/13678754/24528751/409107298.jpg