I don't have any experience loading a GL1800 into a pickup. However, I have loaded mine several times into a BigTex open trailer which had what seemed like a fairly long drop-down ramp, maybe 5'. That expanded metal trailer ramp was what came from BigTex. It turned out the length of the ramp was too short as it created a major problem: the break-over angle was too much to allow me to ride up the ramp at idle and maintain foot contact. Luckily I saw this coming very early as soon as I was high-centered and my feet touching nothing and gassed it up the ramp without dropping it. The other thing was this trailer had no type of chock for the front wheel. The Condor front wheel chock is what I use now in a different enclosed trailer. I bolt it down when I use it. It is so stable you could place it next to the front of your bed, load the bike in it (it has a cradle that hugs the wheel), and then tie down the forks and wheels by straps to each bed side and you will be stable.
Yeah, I wouldn't load it on a pick up unless I had a loading dock or something that was level to the bed of the truck. Call u-haul and schedule a 5x9 motorcycle trailer. It's worth the 40.00 to rent it for a day.
I have loaded my Harley Ultra and my BMW RT in my pickup truck many times. I have a Black Widow 10’ ramp. It works great. It is about 3 feet wide, so you can put your feet down on it. It is curved so you won’t bottom out when loading.
Don’t be afraid of it.