I think the best area for horsepack fishing is the northern portion called the Lake Plateau. Even though it is at about 10,000 feet, is has good horse trails going up to the plateau, and once you get to the top, there are lots of lakes within easy reach. The advantage is you have different species in different lakes, and if one isn't hot, you aren't stuck with trying to go over a pass to get to the next one. The best access is from Big Timber on I-90. From there you go south on highway 298 past Mcleod and on past Natural Bridge State Park. The road is variously called Old Boulder Road, Boulder Road, Main Boulder Road, and NF6639. Just don't veer off onto East or West Boulder Road (kind of like Peachtree in Atlanta grin). As for guides, I think the Big Timber Chamber of Commerce or the Montana guides association would be a good place to start. I always backpacked without a guide, and any I might have known are probably retired by now.
Here is a good overall map of the roads leading in. The Boulder road runs down the long club-shaped corridor that splits into the wilderness from the north.The plateau lakes are to the east/southeast of the road.
http://www.wilderness.net/map.cfm?x...max=-12177884.2574&ymax=5717230.7749
This book is the must have resource for fishing info--
https://www.amazon.com/gp/product/0...ative=373489&creativeASIN=0762742275
Now some info on conditions. Depending on the year, snow may still be on parts of the trails in early July, and it will be cold at nights--sometimes below freezing. Be sure to take longjohns and fleece for layering. In a matter of minutes it can go from sunny to windy thunderstorms with hail or snow. I never left camp without rain gear in my daypack. Mosquitoes can match anything seen in southern swamps, so take plenty of repellent. Grizzlies are there, but not as visible as in Yellowstone or Glacier. Nevertheless, bear spray is your friend, unless you are sure you can head shoot an animal that charges uphill faster than you can run downhill.
By far, my biggest problem each summer was the initial altitude adjustment. Coming from Alabama, it took my body several days to shake the headaches. If you haven't done altitude before, read up on ways to ease the transition.
Now if this all sounds dismal, why would I have spent the best summers of my life there, and returned to scatter my wife's ashes? Well, in addition to the fishing, take a look at this...
http://www.dougroanephotography.com/Nature/Montanas-Absaroka-Beartooth/i-CsB3F68