tires/snow rating / not worry? / chains are solution?

Isn't any tire that comes on an F350 LR E?

If you plan to venture into the possibility of snow on the west coast you may as well get fitted for link chains for the truck and at least cables for the trailer. Carrying chains is often required regardless of tire rating.

If you are not satisfied with Ford's choice of tires talk to the saleman about upgrading, he will be more than happy to do so. Of course it will be on your nickel so shop around, an independent tire shop may do better regarding price and selection.
If you do go with chains don't cheap out, a broken cross link or cable will beat the daylights out of your new truck and likely tear out a brake line. Also make sure you know how to properly install them. Having driven on snow for more than fifty winters I would suggest you will probably never need them unless you plan to drive in extreme conditions. If you are not experienced in winter conditions learn to lighten the right foot especially on the brake pedal.

Snow tires on all four wheels keeps you from needing chains most of the time. When roads get bad enough to need chains on 4wd vehicles, most roads get closed.

If you are towing a trailer, you may be stopped by the Highway Patrol and forced to use chains even in moderate snow conditions with 4wd.

I don't like using chains, because they can beat up your wheel wells and require low speed operation, but I carry two sets for all four wheels when in the backcountry. Fall hunting can you stuck in places that are hard to get out of without chains.

You need to care if your tires are snow rated so the Highway Patrol will let you pass. The sidewall needs to mention snow, M&S, all season or some other buzzword to qualify.

They will be M&S rated, which satisfies the state chain law. Most all truck tires are these days, especially on a 4x4.

You don't get a choice of tire brand from Ford, but that doesn't mean you won't know what you're getting. They are consistent within a model year. So just ask what they will be for the options you are purchasing, or take a look at a similarly equipped truck. It isn't a big mystery to solve.

The FMC order guide gives a great deal of tire info. You can download a copy from any number of sources. A smart buyer always finds that and studies it before ordering a truck.

I always carry chains. In CA, the first stage snow event is as you say, 4x4 with M&S tires or carry chains. Next stage is must have chains. Then must install chains. And lastly, shut down completely for non-emergency vehicles. Best to just have chains ride with you at all times, even if they are just the cheapo cable type.