Short-step bed weight

[Bullseye54]

I have a 68' gmc short-step that I swaped to truck arm suspension & did a 4/6 drop on,along with 4 wheel discs swap.I'm trying to set everything up as far as ride height & see if I need to notch the frame,without putting on the bed.I want to add the right amount of weight to the rear frame.Does anyone have a rough idea on the bed weight?...........................Bob