Check the solar controler and see if it has a Li setting. if so thats all you need to do. as for a isolater, but a DC to DC charger.. renogy makes afordable ones in 20amp 40amp and 60 amps so you can pick how much of a load you put on your altanator. this would let you run the truck on a night time call out and keep your battery topped up on longer calls.
do you know what battery is installed right now? if it is a normal rv type battery that comes with the rv from the dealer then it is probably an 80Ah combo deepcycle/starting. one 100AH LFP battery will give you more than twicw thew availble power you can use with out shortining the cycle life of the battery. you could put two in there and have an increase of about 5x usable power for aproximatly the same weight. if you don't plug the camper's converter in then thats all you would have to do, depending on the age if you do plug in you may have to update the charging section of the converter to one that is also Li compatible if it isn't already.
