I posted this on the Old GMC site a while ago.
Anyone needing to replace the brake light pressure switch that screws into the rear of the master cylinder, NAPA'a part number is SL113. Price is $17 and it is made in USA. There listing is for 1936 to 1946 GMC.
The master cylinder is the same for both Chevy and GMC
Last edited by dunfire; 03/09/2013 4:19 AM.