I guided on the White and Norfork for a short while. It's not the size-producer it once was, but there are still monsters in there.
This big 22 pound brown was caught last spring:
And I've seen browns even bigger than that swim under my boat.
A world record brown came out of the Norfork in 88. It was 38 lbs 9 ounces. Less than a week later, a kid caught a 34 lb 8 ounce fish.
As far as numbers go, those two rivers are difficult to beat. Between the state and the federal government, millions of trout are stocked in those two rivers. That includes the browns as well as rainbows, brook trout and cutthroat (though the latter two are much less plentiful). And there is also some natural reproduction. There are two major lakes there that hold big white bass, striped bass, black bass and catfish too. And there's the national fish hatchery below the Norfork Dam which is open to the public. You can see some monster trout in those raceways, and feed them.
Trout fishing occurs year round. You may run into a more difficult time booking rooms and guides in the summer months, but you should be able to find something. Big browns are most often caught in the early months (February is good) or in the fall (November); but big fish are caught all year long.
A good place to stay is Gene's Resort. It's right on the bank of the Norfork. You can get a room/cabin for a good rate. Their website is
http://www.norfork.com/genes/ As far as guides go, I'd recommend contacting Cotter Trout Dock. If you tell them you're after big brown trout, they'll help you out. Otherwise, the focus will probably be large numbers of rainbows. The bait, rigging and locations are entirely different, so make sure you're specific. Their website is
http://www.cottertroutdock.com/ They have a number of guides. Here's a big brown caught recently on Bob's boat:
If you just want to catch a lot of trout, you can wade in some areas. But beware, as the above poster said, flows increase rapidly. If you want to be safe and have the best shot at some big fish, you should hire a guide.
I'd also recommend taking a kayak or canoe float trip down the Buffalo national river if you get the chance. It's full of big gar, pike, etc., and it's quite beautiful. Here's a pic:
The Red River also produces a number of big fish, but it's a few hours away. Unfortunately, I don't have a lot of info on it.
I hope this helps.