I recently completed an upper tail gate for my '57 2 ton grain box, I wanted to use 5/4 'cuz the lower gate is 1 inch, I'm glad I ended up using 3/4 weathered barn wood. With the gate at 7 feet wide and 32 inches tall, 2 inch wide steel straps, 2x2 hickory stiffeners, stake rack hardware on the corners, it's heavier than I expected.
When I finally get my truck back on the road I plan to make new side boards and probably a gate but plan to make them removable with my skid steer and some forks perhaps in two sections due to my bed being about 15ish feet maybe more or less so any sides that I make will be really heavy.
