Hitch classifications aren't always exact which is why you'll see varying capacities among them. Like you noticed the Class III # C17304 has a 5,000 lb capacity and the Class III # 13703 has a 3,500 lb capacity. My best advice is to not get too hung up on the class and instead determine if the capacity is enough for your application. view full answer...
The Curt multi fit hitch part # 13703 would work great for you as it is a multi fit RV hitch that fits 22-72 inch wide trailer frames and has a 350 lb tongue weight capacity. This will work great with the Hollywood Racks HR1700 # HLY64FR that you referenced. view full answer...