You are right, it is not a good idea to try charging batteries that have different charging parameters.
A 6 amp charger will not bring a 50% depleted 105ah battery up to 100% charge in 8 hours. Get yourself a 15-20 amp 3 stage charger and you should be good to go.
2007 Surveyor SV230 - 200 Watts Solar/MPPT Controller - 230 AH Battery Bank - 600 watt PSW Inverter - (2) 2000 watt Inverter Generators - LED Lighting - Boon Docking 99% of the time.
2009 F150 - 5.4 Litre - 6 speed - Tow Package