Couple of questions?
Have you considered east-to-west?
What's your touring style - miles per day?
Camping mostly - motels only?
For an average rider, 10 weeks is ample time.
So if you left on April 1, you would finish by June 10 with time to spare.
Have you considered other possibilities?
It sounds like you plan to stick to established routings - is that essential?
ACA will be publishing its "Route 66" maps soon.
Your time frame and plans make using parts of this route advisable.
Get out your map and trace a line from Barstow, Calif, to Williams, Ariz.
(Basically following I-40 - but then look for old Highway 66 nearby.)
It's a historic highway with lots of kitsch - not quite as hot at first.
But you do have a long stretch thru the Mojave Desert and will need to plan.
The ACA Route 66 maps will start in L.A. and take you over Cajon Pass.
If you prefer, there is an easier grade with far less traffic out of Ventura.
It follows the Santa Clara River via Santa Clarita and Palmdale to the Antelope Valley.
BTW - early April is the best time to see the wild poppies at the Antelope Valley Preserve.
Might I also suggest connecting the Grand Canyon Connector to the Western Express
Via Monument Valley - i.e. from Cameron to Kayenta to Bluff.
Monument Valley is fabulous to bike thru - the stuff of Hollywood images of the West.
By then it should be late April, if you stop to smell the poppies and visit the canyons.
It won't be a cake walk to get across Colorado, but you can use flexibility and do it.
Or - - you can stay lower via northern New Mexico and hit World Heritage sites like Taos.
I've biked 100,000 miles - mostly in the West - be glad to be of assistance.
My advice would be to make your choices for your tour, first -
Then see how closely established routes fit into your needs and preferences.
Most of the Intermountain West roads are easily bikeable -
Moderate traffic, often with shoulders. Clearly near Vegas or Denver it's different.
Services, esp. so early in the season, may be few and far between - esp. in the mountains.
So you will need to use care in planning - but west-to-east is certainly doable.
The Blue Ridge Parkway and Skyline Drive might make a nice finale in the East in early June.
Best - J