Older RV's (more than 10 years) usually have the drawer/s under the cook top. Those drawers are removed and the cabinet pieces cut out between the drawers to install a Oven/cooktop. They usually made sure those drawers will be the same size as the Oven as they did not make cabinets for just a Range only. They did not want to make 2 separate cabinets because they did not know what the final option would be(Range or Oven combo). You will not be able to use your old Range top. You will install a combo. I would NOT buy from a salvage yard but buy a NEW Combo unit. There is NO adapters needed for the LP. You use the same LP line that is on the Range Top and that LP line will connect just as before. The cabinet will NOT have to be beefed up. The Range AND the Oven are supported by the counter top. Most OEM's will install a wood panel UNDER the Range or Oven and you can use the existing panel under the range and drop it down far enough to mount under the new Oven. Doug