Another thing with the deep cycle is you'll need to charge it periodically independent of the vehicle. A charger that's specific for AGM/deep cycles is best.. the alternator will keep the deep cycle topped off and will measure full charge, but it will drop quickly, faster than you think it should. Giving it a good trickle charge will slow that down though, something to do before a big trip, etc.
A few of us here have the C-tek chargers, if you search for that there's probably more battery theory about the differences. hth!