Hello Jodi,
Welcome to the ACA Forums. If I understand your question correctly, you would like to ride from Santa Monica to Virginia using both BR66 and the TransAm (TA). While I am not doing that ride this summer, I can almost guarantee someone has. The reason I say this is that I live in Tulsa and have had several WarmShower guests who have done something very similiar, i.e. started in NYC, dropped down to the TA near Richmond, VA, then dropped to the BR66 in Springfield, MO.
However, you mention Pueblo and the Western Express (WE). Do you want to connect to the WE from BR66? If so, approximately where do you want to connect and what do you want to do accomplish, i.e. avoid mountains, go to a specific town, shortest/fastest connector route, etc.? Also, what time of year? Again, this has been done, i.e. connect to the Grand Canyon Connector (GCC) in Williams, AZ, then the WE in Cedar City, UT, and then the TA in Pueblo. However, this is a fairly mountainous route, though scenic. Others have just broken off the GCC near Tuba City and reconnected to the WE at Blanding, UT, or in Delores, CO, though this is a lot of remote and unpopulated areas so may require stealth camping so plan accordingly. Finally, some have broken off BR66 at Gallup to head north to Delores. This too is isolated but for only for about 2 days. Also, most of these routes may have closed sections from late Fall to late Spring due to snow.
However, if all you want to do is connect to the TA, I would just ride BR66 to Springfield and connect to the TA there.
Tailwinds, John
P.S. It is best if you post your question only in one place as the answers can get scattered and the post can be hard to follow.