If the frame members are further apart than 72 inches, we don't have a frame mounted hitch that would work.
If the fifth wheel has a 4 inch square steel bumper, a bumper mounted receiver like # E-100 would be a good choice. The hitch has a 350 lb tongue weight capacity which would be limited by the capacity of the bumper if its lower.
If you click the link, you can see a video featuring the bumper mount hitch I recommended. view full answer...
Based on the brackets you have near the suspension of your Open Range 3X 375RDS 5th wheel trailer your best option for a shock kit will be a Lippert kit that doesn't take up as much space as the Roadmaster kit you referenced.
For that you'd want the # LC281255 for if your trailer has 3,500 lb axles that are 2-3/8 inch in diameter or the part # LC281281 which fits axle diameters of 3 inch like what are found on 5,200 to 7,000 lb axles.
Also thanks for clarifying what the brown foam was.... view full answer...
We don't have the specs for your specific trailer's wheel pilot hole. There are two common sizes for the just over 3 inch caps. We have the 3.19 inch option like # 319EZ and the 3.33 inch option like # AM90195.
The best way to know which you need is to use a digital caliper like # PTW80157. view full answer...