Most of my experience has been with ag trucks, both gas and diesel. They used to rely on gears to get up and down hills. I'm now driving a newer diesel pickup. There is a night vs day difference. I watched my father go from gas to diesel and campers to 5th wheel trailers while travelling all over the country. A newer diesel is much better than gas. It will pull you almost anywhere and most diesels will last a lot longer while getting better fuel mileage. We ended up with Dodge to get the Cummins engine, but I can't say much about other new trucks. My father also had Fords, and I remember him saying that one bought Dodge for the drive train and others for the interior. You didn't specify new or used, just that cost wasn't a concern. Have you actually priced new trucks and trailers? I suffer from sticker shock just hearing about these prices. And it is hard to take the immediate loss in value when a new truck and (especially) trailer is driven off the dealer's lot. You don't need 4-wheel drive to pull a trailer, but it can help when roads are slick and to back up-hill into a parking spot, and the low range that comes with 4WD helps when you want to go really slow. I don't know if this has changed with newer trucks, but there is a difference between 4-wheel drive and all-wheel drive vehicles, and using 4-wheel drive can affect turning radius. One thing that I didn't see mentioned, and may now be standard equipment, is an engine brake. Trailers will push you down-hill, and it really helps the brakes a lot on both the truck and trailer if engine compression can help keep speed under control. One final word about pulling any trailer is that stopping is most important. You don't want to see the trailer sliding by you with the truck brakes locked. So both the trailer brakes and brake controller are very important, and setting the controller so that the trailer brakes work as intended is time well spent.
JRMunn