I've always pushed or rode the bike up an incline, backed the truck up to that incline, and pushed the bike, on the ramp (I made one 8 feet long) onto the bed.
The one time I loaded with the same ramp from a level location, I caught the back of the fender and bent the struts (Big Twin FLH). Probably would have worked fine with a bobbed fender. You generally catch the bottom of the frame on the bike as well in that transfer point where the ramp meets the tailgate or truck bed if you drop the tailgate, but it can be manhandled up and the frame itself protects everything from damage.
You have to watch that the ramp doesn't move off the truck bed or tailgate, that can happen and you don't want that kind of disaster. Might mean a trip to the hospital and a cast, or worse.
I also built a motorcycle work stand, I think it is 24" tall, out of 2x4's and a sheet of plywood, 4x8. That worked great with the 8 foot ramps, and although it was heavy and needed two people to move, you could place the work stand in a suitable location, use the ramp to move the bike on the stand, and then once again (like using the incline) moved the truck in place, using the ramp, move the bike from the work stand to the truck bed.
Probably not a solution for you unless you want to work on the bike in your shop at a comfortable height, but if so, worth considering building one. I have to say it was over-engineered in a Caveman sort of way; if I was to do it again I'd make it lighter, as it doesn't have to be as heavy as I built it to support 800 or so pounds. Maybe use ripped 2x4s (2x2's) instead, for example.
The Home Depot solution, using 2x10's or 2x12's (floor joists) that are more than 8 feet long can work, but it's a narrow perch unless you use four or more side by side. I've used two twelve footers, and there were no disasters, but it's pretty narrow.
