Oasis Bob,
I am going to fire a big scatter shot at you, but be ready.
I do it all when planning a serious excursion.
I usually start with my go to with is Street Atlas 2015 (the newest but was out of date when new). If you can find a copy, it is great but it has a very steep initial learning curve.
¿¿Why do I do this??
Because I have laid in my speeds, preferred stopping time and tank range.
So, as soon as I say "Here" to "Here" it draws a path, tells me road hours and lays out marks for ONP and fuel stops.
So, I put in Portland (right on the river)- to Mount Rushmore and that is 1252 and 22 road hours.
So, I added Fishing Bridge at YNP an FHU park and now we see 1310 and 24-1/2 rhs.
Put in Silverwood south of Athol and we now have 1355 and 26 rhs for the whole run. So, the diversion to the amusement park was not a killer.
It is 397 to Silverwood. That is a long day.
Another 498 to Yellowstone. I would plan to break this up unless you can co-drive.
And 460 to Mt Rushmore. Ditto
I also have an address book full of stops I would like to make, some are dreams of someday.
In your case, you really should consider the Museum of the Rockies (Look up Jack Horner - you want to see that). It is about 6 miles off the planned track, a couple or 4 hour stop 6 hours from Silverwood and possibly a place to find a stop for the night.
From there it is 2 plus hours to Fishing bridge.
From Yellowstone it is 459 to Rushmore. There is also a good stop at the museum in Cody (You will never guess who that is about).
Crossing the Big Horn makes it a day.
You will want an ONP stop about Upton or Osage.
Rushmore is a good stop, but not a real time killer.
As you unwind from there, add Crazy Horse as a stop. It isn't cheap, but it is good. The restaurant there is great and tell them you plan that at the gate. They might give you a break on entry - used to.
This all took about 20 minutes for me to assemble. Before I commit to it, I will check all the individual legs on AAA online (free) and/or Google Maps because SA is sooo OOld.
I will also use all the area guides and AAA guides (now online so unavailable on the road), and pull in paper maps also from AAA. Paper maps still work when the electronic stuff shoots *****....
Unfortunately, I have not found another - newer package that can do what I just did. Many can sort of do most of it. Some only want you to stop at cramp grounds that they know about. And none of the on-line can adapt when you make changes on the road. I keep looking. I like this because it keeps track of when we last fueled and suggests where to think about it again. (This is where Gasbuddy comes in.)
I hope this was a help.
Matt