Best route may depend on where you plan on camping. We came from the same direction as we started in Iowa. We boondocked in Billings and from there Google had us heading north. Here is the route we took:
https://maps.app.goo.gl/LdGNyBKg4vqj4bzZ9 Glacier is massive so depending on the side of the park you are staying nearest may change the route you want to take.
The campground we stayed at (
https://www.glaciercampground.com/) worked well for us. It had power and water at many sites, sites were nestled between trees, and was almost within walking distance to the West Glacier entrance. The mosquitos were legit though and we ended up buying a screened in porch\tent for the evenings. Hard to recommend any place since everyone camps differently but we would stay there again if we couldn't get a site in the park.
We went 2 years ago and that was our first big trip pulling with our 350 diesel. While I wasn't worried since we had the bigger truck I too was wondering what the drive out there would be like. My only puckering moment came on our way to Billings. We'd drive along these long stretches of constant incline grade and when the oil and trans temp hit a certain temp they switch for a gauge view to displaying the actual temp. Had never seen that before so I'm immediately thinking we are about to overheat, but turned out we were fine. Leaving Billings we drove up a switchback but that was probably the steepest part of the trek and you are driving 20mph. Our friends were in a class c flat towing a jeep and they made it just fine. We'd just make it to the top of the hill faster than they would so I'd say worse case you have to drive a bit slower.
We loved Glacier and I'd go back in a heartbeat! Like I mentioned earlier the park is huge. We did the iceberg lake hike which starts from the East entrance which is about 90-100 miles from our campground if you don't\can't use the going to the sun road. We found that where we stayed steered us to which parts of the park we most visited.
The going to the sun road pass is key and can be a pain point for the trip. We got ours the day they were released for the week we were staying there. The catch was they were only good for 3 days so you have pick which of your days or try to get multiple passes. Turned out that year the road opened unusually late so some of our pass days were wasted because the road wasn't open. We tried getting a pass the morning of and were unable to so I would try your best to get them in advance.
Here are some views that await you(the nature ignore the people):
https://photos.app.goo.gl/szW4W24k1yT6a9f38 https://photos.app.goo.gl/GW9psjCYDiVWDKzD6
If you or anyone reading this thread has additional questions happy to share more.
Safe travels,
Pete