If you are thinking of installing an inverter
NOW would be the time to do it ! And what you want is a combination inverter/charger/transfer switch. Several manufacturers make them, but I like
Samlex. They are easy to install because all connections are made at one point and have the similar "intelligent" charging of the Progressive Dynamics.
(What they called "grid power" is your shore power connection.)Once this is done, disconnect the WFCO converter and hook the DC distribution panel directly to the batteries, bia a fuse of course.