The seatbelt part of your question caught my eye.
Please note that RV Furniture doesn't necessarily come with seatbelts. Camping World sells Flexsteel furniture, so lets use Flexsteel as an example.
A Flexsteel sofa will not have seatbelts. It can accommodate seatbelts, but they are not attached to the sofa. Instead, the seatbelts are bolted to the floor under the sofa, and the sofa will have openings at the rear to allow the seatbelt(s) to come up through to the seating area.
Similarly, Barrel Chairs mounted on a fixed pedestal (top may rotate but locks into position), can have a seatbelt, but they typically do not come with the chair. The seatbelt is bolted to the frame of the chair or pedestal below, then passes up through small openings in the back of the chair to the seating area.
In summary, seatbelts are usually sold separately, and should be available from Camping World or whoever you buy your furniture from. If not, your local auto parts store should sell some form of after-market seatbelt that will fit your needs. … or just do a Google search and you’ll find places like this:
http://www.seatbeltsplus.com/
Free standing furniture – Euro Chairs, recliners, and swivel rockers – do not attach to the floor, do not have seatbelts, and should not be used while the vehicle is in motion.
Another source of Slightly used and new furniture is McKinney RV in Red Bay, AL.
www.mckinneyrv.com I haven't used them... Yet!, but they seem to have a large selection. I suspect McKinney RV buys alot of the excess stock and overrun material from Tiffin as Tiffin is also in Red Bay. Take a look and decide for yourself.
Good luck with your project!