Cletis: on GMC trucks (older model, as stated by parts manual, go figure what year that might be) the serial number of the frame is stamped on the front tip of the passenger side a little bit to the front of the radiator support. I'll take a picture tomorrow of my truck (FC 101 and the number). Just found about it a couple of days ago while removing 60 years of grudge of the frame. The caution plate (.not serial number) was located in the right side in the cowl and there was a cab or body number located on the cab floor of the right hand door lock post (discontinued according to the manual on May 1949). Later models have the caution plate with the serial number on the left hinge pilar. This is for GMC trucks