I've found a 90" long & wide deck to work well on a short box. I made mine so it could fit two old M8's on it, width wise. Knowing full well the newer sleds are all narrower. It sticks out 7" on each side of my cab on an older (1996) Ford. This doesn't make it feel wide when driving. The mirrors stick out at least that far. I didn't want to deal with folding sides, but you may want them (they're heavier so I nixed that idea). For length, 90" kept the receiver hitch even with the bumper, yet its not so short the front skid shock is collapsed.
I made a lockable ramp storage slot and small bin under the deck for holding hitches, chains, straps.
This is on a half ton truck, so weight was a top priority. Mine came out very near factory box/bumper/tailgate weight. With your HD 3/4 ton it's less of an issue, but don't let people convince you it needs to hold a house.
I don't have many photos. The paint picture was early on in brainstorming. I ended up hand drawing the actual plans. The front of the deck tapers to match the cab width (45 degree taper). There are bolt on sides, which are simple 4" wide 1/8" thick strap steel, with holes punch every 18" for lot's of tie down locations. You can never have too many tie down points! I added a D ring up front, centered, and another in the rear, centered. The headache rack matches the cab width.
The ramp is a tri-fold I made that's 90" long and around 46" wide unfolded (15.5" wide and about 4" thick folded). The deck sits ~40" off the ground, and this makes for a nice ramp angle. I originally used a cheap aluminum tri-fold with glides riveted on (think it was 5.5' long), and it was a bit too steep, not to mention weak.
I can get more photos. I'm not a pro fabricator or welder, and anyone who is probably laughs at what I did, but it works well. After 2 seasons I wouldn't change anything except enclosing the ramp storage. On the nastiest of weather days, the ramp can get pretty loaded up with snow/ice/grime.