There are just two LA cars on the Texas Eagle, one sleeper and one coach. The Sunset consist currently contains one sleeper (no transdorm), one full coach, and one coach/bag. It is not two Southwest Chiefs put together. That was a poor assumption.
The entire capacity of the Sunset/Eagle combined consist, if every seat and every berth were filled is 298 (44 for each of the two sleepers 74 for each of the two full coaches, 62 for the coach/bag). Subtract out roomettes for two SCAs, two Coach TAs, the cafe LSA, and an LSA, SA, and chef for diner and that reduces the capacity by 16 (8 roomettes). So the absolute maximum passenger capacity is 282.
I welcome any corrections to my math.