Old 1949 data books show a range of estimates from ~5400 to ~5900 lbs curb weight for those 49' 6400 series, but the tilt bed isn't clearly listed. Many of those old AD 6400 trucks had aftermarket beds so its hard to tell how much extra steel and stuff added weight.
When I last had my 6400 w/Knapheide hauled I told my friend ... "Well, its about 6000 lbs or so"