What size 6v is close to the same size(I don't have a lot of space between the trailer MD the propane tanks)
You should contact Costco & get exact dimensions of the 6-volts you want.Will my WFCO 35amp power converter work with the new battery system.
Yes, It will work.Do I need an additional battery charger when its sitting in my driveway (its always connected to shore power when sitting at home)
No, you do not, but you should verify the exact model of the converter & it's charging profile & maintain water levels in the new batteries.READ
THIS