Chuck, Since it's a 1947, the only place I could find a possible reference to your measurement comes from the
1947 Chevy Truck Data PDF from the GM Heritage Center. The pic below shows the "top of cab floor" to "top of frame" measurement to be 1-7/8" from what I can see.
If you measure your "top of floor" to "bottom rear edge of the cab" and take that away from the 1-7/8" measurement, that should give you the distance between the top of the frame and bottom of the rear cab edge that you are looking for. Hope this is clearer than mud and helpful???
