Hey, does anyone have dimensions for a heavy duty shop crane?

I have a 3ton long arm jack and want to build a knock down shop crane instead of buying one of those fold up deals. My shop space is pretty tiny, I want to make one that comes apart into separate components and stand them up in the corner or oil drum. I had detailed drawings of a dandy unit I rented once, but lost the darn things and dont want to drop another $50 on a rental when I can buy steel with it.

I'm more or less concerned with the footprint, overall height of the mast, length of the beam or arm (fully closed and fully extended) and its service height (low position). If anyone can help me out with some of these dims, I can work out the rest 

Thanks in advance