I think you have misinterpreted Trojan's recommended charge rate. Look closely at diagram 4 in Trojan's User Guide.
The recommended charging rate is 10 to 13% of the 20 hour amp hour rating, not C/20. It is pretty much the standard charge rate of all FLA batteries or C/10. So the minimum charge current you are looking for is 26 amps up to 34 amps. With FLA you want a high enough charge rate to make the batteries bubble and boil a bit to keep the electrolyte moving to prevent stratification. So yeah being your pack is 120 volts you will likely need a 240 volt charger, and that charger will use a a dryer type plug.
