Are you sure you can pull a 38' trailer with a F-250. This seems like you might need to upgrade to the F-350/3500 HD.
I just don't want you to become a member of the "I didn't buy enough truck the first time" club, there are too many members in that club on this forum already.
Anyway, I really like pulling my camper with the F-350 diesel. I completely understand not wanting to spend the money for the diesel and worrying about the repairs. However, what I did was spend the money for the Ford extended Warranty, the Ford warranty covers almost everything and it is honored by every ford dealer (it even covered the gas struts for my hood). If you go this route, make certain you are getting the Ford warranty and not some other warranty the dealer wants to sell you.
Good luck and really check the towing numbers on the actual truck, not just the spec sheet.
You can pull a 315 with the F250. The powertrains in all of the Ford SD trucks are the same. The difference is in GVW. This is the key thing to consider. Also, the diesel consumes about 800lbs of GVW, as it (and its associated systems) are much heavier than the gas drivetrain models.
My F250 is a diesel, but I also have the high capacity tow package which ups the GVW from 10,000 to 10,800lbs. My truck weighs right at 8,000lbs bare, and about 8,600lbs loaded. That leaves me about 2,200lbs to “give” to a trailer. This is more than enough for the 315, which can range from about 1,400 to 1,600 lbs tongue weight. Some report even higher tongue weights with this model.
However, 2,200lbs to give is too light for most 5th wheels. A similar gas F250 would have about 800lbs more to give, or around 3,000lbs with the 10,800 GVW package. This is smaller 5th wheel territory.
The F350 is a better choice if you might be going for a 5th wheel some day. Typical GVW is 11,400lbs I believe. Larger 5th wheels would be dually territory.
The moral to the story is, pay close attention to these weights. Specifically, tongue or pin weight is usually the limiting factor. Also, manufacturer specs are notoriously optimistic. Door label cargo capacities on the trucks are “as built” from the factory. Everything you add is excluded. Trailer tongue weights are the same. They don’t even include batteries, propane, or any water. Never mind camping gear, food, etc.