The Cat 305 has a weight of 13,000 lbs (full fuel and wide bucket). The dump trailer you need will have a empty weight of 8-10,000lbs and be 18- 20' long and you need heavy duty reinforced D-rings and chain binders. You need the longer trailer to be able to keep the boom low under 14' height bridge clearance. You likely need a gooseneck style trailer with two 10,0000 lb axles and GVWR of 25,000lb and of course a one ton dually 3500 size pick up, or class 8 truck with DOT numbers, and a class A CDL. Even if you could get it into say a 14GVW dump trailer, the trailer has a weight of 6,500 lbs, so your load is still only suppose to be 7000-8000 lbs. So you would be way, way over loaded and extremely dangerous and the 14' length would mean the boom is too high or sticking out of the dump box. The boom must have it's own tie downs to stop the boom from swinging side to side to be legal. You could try something like a BIG TEX 7×16 DUMP TRAILER 8 TON bumper pull 16 gvw, but I bet you would bend the loading ramps, and the excavator wouldn't fit real well and tie down and the trailer wouldn't last.