Just an update - I went ahead and went with the tractor style T pins - and used a ledge under the bed to hold them in place while I installed spacers and the pins in the box. And I have my chainsaw in the box - which is upgraded from my last post to a 58" x 20" x 18" toolbox that my friend gave me.
(Traded the cross over and side boxes for an old school diagnostic system on top of a vintage snap-on toolbox - to which I gave my mechanic friend. This is the kind of system, that if it works, will help him do diagnostics on pre-obd vehicles and equipment.)
So - my dilemma is still - storage...
I could just leave my chainsaw stuff at home, but I'm typically working on any 3 things at any given spare time - construction/mechanics/logging.
3 options:
1) 2 chest type 58" toolboxes facing outwards towards the front of the bed. That allows the full 9' to the headache rack in the middle, but only allows 3' 10" from the end of the bed to the end of the box. And - the toolboxes are 4" past the gooseneck ball, but I think they are low enough that that won't be an issue.
2) Purchase a 72" x 24" x 24" Knaack box and mount on the front of the truck. Might C-bolt it to the headache rack and leave the casters on it to allow for space underneath, and allow me to move the box around if I deem it necessary. Have even considered building rails so that if I wanted to use it to prop something up at the tail end of the truck I could... Doubt rails could stay clean, so don't think that's really an option.. Down sides - potential blocking of vision out back of window, and it's 1 box with everything - so a little more difficult to organize and keep organized.
3) Purchase 1 or 2 36" underbody boxes and mount them perpendicular - using them as vertical storage cabinets at the front of the bed, on either side of the 58" tool chest. The biggest downside I see with this is that the underbody boxes - regardless of where they are mounted, don't seem to offer much storage space. And could block vision on the passenger side.
Any thoughts? Anything I'm not seeing?