Jinx, what you ask has a lot of variables as I see it. Personally, I tend to overdesign things. So, I am going a little conservative here. But, a starting battery is just that, good for starting the truck and nothing else. If you are discharging it, you have other issues. I like to think of the starting battery as my garantee to go home after the day. Would it make sense to have only 1 battery in the truck, run some big things off of the battery that will lead to its draining to only not be able to start the truck to go home? Hence why you will find that I am a big advocate of dual battery setups if you are planning on lots of use of battery power only. if the engine is running, then the batteries are not an issue since they are there only for large current surges (if you are hitting this point, then you need a larger alternator).
As for survivability from discharges, starting batteries will handle minor discharges (less than 20% of capacity) with relative ease. But, you start going much more than that and you can plan on the battery having a shortened life span. Will it do it. Of course. But, how often do you want to be replacing batteries? Ironically, if you have a deep cycle (a battery meant to be cycled between full and zero capacity over and over), if you don't cycle it, you can ruin it. They require a deep discharge atleast monthly to maintain their health. Will they survive without these deep discharges. Sure. But, you are again shortening their lives by not discharging them.
If you are interested in trying to figure out the amount of discharging you would be doing, let me know. I would just need to know the wattage rating of some of your typical components and then I can give you how to figure it out. If you know how to figure out amp-hours, then you can figure this out yourself.
I don't want to go in way over your head, but sometimes what appear to be a good idea can be done other ways cheaper or must be done a very specific way to garantee you get what you are after.