If you want to avoid the strain on the truck, avoid the Bighorns. Without adding a lot of miles and taking the Bighorns out of the equation, go through Casper. Just use Google Map with Custer SP, Casper, Fishing Bridge as your points and it will route you the correct way. We had originally planned on going the Buffalo-Woland route in 2000 when I was pulling a 7k 30'TT with a 92 F350 but had to take the Casper Route because of wildfires along Hwy 16. It was an easy pull and we spent the night in Casper to break up the trip. In 2005 we came out of Yellowstone and did the Woland-Buffalo route back over to Custer but this time with a 35' 11k FW but pulling with a Dodge Cummings. It was an easy tow for the diesel, but I was so glad we had avoided it in 2000 even though I'm experienced pulling heavy loads in the mountains.
