Your slide in has it's own power source, your other equipment is screwed to the truck and is not part of it. I would ask your broker for a letter from the insurance underwriter verifying that coverage. I seriously doubt you will get it.
30 years ago, I bought a new
Butler and ask our broker to provide the underwriters verification that the truck and unit would be covered as one. They did provide it in writing. I hit a deer with that truck and the insurance adjuster deducted a double deductible and treated it as a separate unit. I called the state insurance department and they made the insurance company honor their policy.
I would suggest taking out the inland marine with replacement cost. If you have a loss, it will be much easier to settle.