Its easier in a slide model.
A boat swivel pedestal might work . You have to be careful of your overhead cabinet/bunk headroom once the seat is installed.
Most of the time , there is a storage cabinet below the base of the dinette or a furnace. Therefore the OEM construction probably has to remain and the new seat must be installed on top of it .
I found it easier and cheaper to make a simple mod that just happened to work out very well for me. Thinking of resale value , I still have the OEM bed option if I should need it . I kept the OEM table, if I or the next owner ever need it.
Here are the pics on this thread:
http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27170874/gotomsg/27171043.cfm#27171043