Do ya want it for haulin...or lookin purty..??? Ive built several beds..but Ive always used metal.. Channel Iron typically. wood rots out to quick and wont hold up to uhhhhhhh sharp haulin, (rock Steel).. A good way to hold it down is with at least half inch all threads with a top and bottom piece of metal for the all thread.. around the frame and stringer.. Just two metal straps (one on top of bed frame, and one on bottom of truck frame) with a hole on each end for the all thread,,and tighten them up.. 5/8 works better... that way if it tries to shift it just gets tighter.. id also use a piece of 1 inche hardwood on top of the frame between the bed and frame to keep it from wearing thru the frame,,, dont weld to the frame especially on newer trucks unless you know what your doing.....Dont drill through frames either especially the top or bottom frame rails.....
