Most folks here already know I won't kit the long road without my 'Jammer. What some don't know is: also with my Lowers attached. At first I thought they were overkill, not real pretty, etc., until I rode 3 back-to-back days of 2700 miles total. After that, every long trip gets 'em back on it.
The seat: the OEM K2 seat was the best on all of the 750s I have ever ridden or owned. Just that one: the later ones are thinner under the butt-bones, and the earlier ones were thinner, period. The K2 and early K3 (with the dropped line along the side, right where the bones are) were the best. I recently obtained a brand new one (won't tell how...) and am working on getting the correct cover for it, for my next long rides.
In the back: it helps a lot if you can have something to rest back against. It can be a pad or knapsack (or her, if she doesn't mind), but should be both soft and firm or it doesn't help much past 400 miles or so.
I'm a fan of the tall gears for the long rides. I have 19/48 sprockets on mine now (with an increased-output engine, though) and it makes 75 MPH the thing of sweet dreams and soft sounds, with 4th gear becoming passing gear on 2-lanes. MPG is higher IF the speeds are over 70 MPH: at 65 MPH it is too tall gearing, makes it feel sluggish and drops the MPG from the laboring. This is with a 4.00 (aka 110) rear tire: with the 120/90-18 rear, the 18T is OK, while the 130/90-18 rear puts it in between the 18T and 19T for the 4.00/110 rear size. I prefer to run 104-link chains, too, as it increases the wheelbase about 1+ inch, lowering the shock from the rear wheel to my back, noticeably.
Carry a spare set of points or points plate, 2 sets sparkplugs, maintenance wrenches for oil changes and chain adjust, and points setting (I use a static light on the road, for the latter). Leave home with good tires, and for long rides, 2 spare tubes. I use an air hose that screws into a sparkplug hole (no, it will not make the tire explode...) in case of flats, also a patch kit, tire gage. I also usually carry an oil change with me, just 'cuz I am picky about that stuff. Can of chain lube.
Install a lighter spring on the throttle return for the dual-cable setup: it is safer by far to have both cables intact. The right spring is at Ace Hardware, about $3. It is just enough to overcome the cable friction, so my [built-in, pre-K3] cruise-control seldom gets used, and my wrist doesn't get tired, either. (Boy, it used to!)
Camera. Water (I like to stop for Mac's iced tea...). Snacks (jerky?) that are salty. No maps (maps are for wimps, IMHO).
Tank bag, if you don't mind it scuffing the paint, makes a terrific way to reshuffle the weight toward the front somewhat, greatly improving the cornering on non-straight roads. Mine has a clear map pocket I sewed onto the top, kept the maps my wife wanted all neatly folded up while we rode...
Tent. Sleeping bag, small tarp (big enough for both under-and-over), my jacket is my pillow.
Gun...
Sort of like on my 'About' page picture in my book? That was a short trip, 2 days to Seattle and back the next week, from Denver.
