Batteries or Converter-Charger

The link above is for the deck mount version, which can be located anywhere, such as close to the batteries. It might fit in place of the existing WFCO "lower portion" They also make a replacement lower portion if you want that to go there. Not sure about 98s vs 89s for that, Randy at bestconverter would know.

http://www.bestconverter.com/Boondocker-Main-Board-Assembly-for-WFCO-8955_c_196.html

There is another option too, same idea but using a PD

https://bestconverter.3dcartstores.com/PD4655-55-Amp-Converter-Upgrade-Section_p_352.html#.UwWMbGeYZjo