Well, 100 is a little tight in the turn on the far end and has some small sites. I know you can list your trailer length as a note on your reservation blah blah blah but if your neighbor across the road has his truck parked in the way or the trash can is in the way too, it can be tough.
200 is the easiest of the three Preferred loops to back into - not many short sites (but some including probably the shortest in all of FW, 201 - I spent a night in it).
300 is so tight it's the only loop to have painted lines on the campsite pavement indicating no vehicles extend past these PLEASE.
(took this picture in 300 on my Halloween trip - see the yellow paint on the ground? 300 is curvy and tight).
If you are okay with a Premium site but like the Preferred location in the Fort, reserve a Premium and put a note on your reservation (have to phone it in) for 400 loop which is just across the street from 100. I had a reservation one time for a Preferred and got bumped out when I arrived to 400/Premium across the street. It was just as close to the dock, Trails End, and beach.
Plus given your trailer and truck size, having a full concrete pad would be good. The Preferred have the gravel tent pads on the back that some people don't like to put their wheels on. And "tightness" is very site specific. 110 is short, interior on a curve, and hard to get into. 125 is very long, exterior, easy to get into (camped in it on that Halloween trip). So "it depends".
I would go with a Premium and a 400 request.
Bama Ed