I didn't realize those linear actuators were so powerful. They must be sorta like an electronic hydraulic cylinder, huh?
Well, you could use the same principal with the tube protruding out the side of the trailer. Fasten/weld/bolt a bar to the protruding tube and attach one end of the linear actuator to it and the other end of the actuator to the trailer frame or on a mount if needed. Only thing I see is the travel you need to get the ramps to go fully up and down. So the bar should be about 6" to 10" long (the protrusion) and should have some extra holes drilled in it so you can reduce the "radius" to give you more or less travel for the ramps. You may only need to rotate the tube 1/4 turn or so. I would clamp it first to find a relatively good position. The closer you connect it to the rotating tube, the harder it will be to rotate but it will rotate faster. The farther out you connect it, the easier it will be on the actuator and it will rotate slower.
(Assuming a constant linear actuator speed)
In fact, you could make a connector which will slide up and down on that protrusion...to increase or decrease the rotating radius. The connector would have a clamping bolt in it to fasten it's position to the protrusion bar when you find the right spot where the actuator will work best. The other end of the connector would be connected to the end of the linear actuator. You might be able to use only one linear actuator that way, if the correct radius allows enough travel and has enough power. If not, you can always add another one on the other side.
As far as being able to adjust your ramps, I would make the ramps so that they can be fastened to the rotating tube in various positions. That is, they should be able to slide on the rotating tube much like a fork lift's forks. Then pin them to the rotating tube which has holes in it for adjustment.
..what about using something like this