Common way to do it 
Just buy some steel channel. They make it in that size. I probably have some here if you’d need a couple small lengths.
If you plan to have a wedge base on the end of the ramp that contacts the ground(to make a low of a drive on edge as possible) consider pinning the ramps to the deck. Pending truck hitch height and/or loading angle of the whole truck + trailer you can sometime end up with ramps that pop up off the lip when loading/unloading.
This happens to Jason Micares’ two car, because the ramp base angle is not meant for the trailer deck height. Ask him what he almost did to the JP car one track day :lol
If you just square off the ends of the ramps and use wood or similar to lessen then approach edge, then you won’t have this problem, but will just have to keep some shim boards in the truck.
Shit paint sketch: Jay’s ramps on two car are on top, single car ramp style on bottom. can see the issue with top ones on pavement if not pinned.
