I had a good email volley with WFCO technical support this morning . Bottom line their converter/charger will work with two 6 volt in series or two 12 volt in parallel . And no problems using FLA or AGM . So the technical concerns are answered , it now boils down to 6 volt vs 12 and FLA vs AGM .
Knowing what I know now I think 6 volt GC2 batteries are the way to go . But I have to confirm they fit my battery boxes . Found a guy an hour away selling new Trojan T105's FLA for $135.00 each . I will get it figured out . Thanks for the help fellas