Interestingly enough, same topic title was in another section a few weeks ago..check out
http://www.montanaowners.com/forums/...ad.php?t=18910
Also check out
http://www.montanaowners.com/forums/...ad.php?t=18917
I agree that your plan for 500-600 miles/day is very optimistic.
I did that route from FL in Nov, and it was a very tiring trip.
A real serious suggestion: LA traffic is really congested. Westbound, the bad traffic begins at Riverside. If coming in from that direction, highly recommend that you "hole up" somewhere prior to Riverside the evening before entering the LA Basin. Timing is everything!!
Best time to come through the LA area is on a Sunday. If you can, on any day, plan to transit the Basin between 1000 and 1330. For weekday travel, I wouldn't even think of hauling an RV through that area between 0500-0930 and 1500-1900 . And I'm fearless...