^^^^ditto. Are you making patch panels. In the large flat areas will measure about 18 g. In the bends maybe 19g. That's how it is on a '56 Chevy Delray.
There is some overlap between the gages, you might check out this thread for help. http://www.jalopyjournal.com/forum/showthread.php?p=8544234#post8544234
chevy metal is thinner than fomoco's 19ga. the chevy's ive messed with (49-67) seem to be more around 20ga. the gauge thickness might be different on the trucks though..