Kato Smoothside Streamlined Passenger Cars

With the exception of the observation car, these models are all based on Union Pacific prototypes (although other railroads may have had similar cars). The observation car is based on a Southern Pacific Pullman prototype. These are the releases that I know of (culled from old Walthers catalogs) -

6-car sets (Coach, Sleeper, Diner, Baggage, RPO, Observation) -

381-106010 Undecorated (1994)
381-106011 Amtrak (1994)
381-106012 Milwaukee (1994)
381-106013 New York Central (1994)
381-106014 Union Pacific (1994)
381-106015 Via Rail (1994)
381-106016 Baltimore & Ohio (1994)
381-106017 Burlington Northern (1994)
381-106018 Pennsylvania (1994)
381-106019 Southern Pacific (1994)
381-106019 Southern Pacific (1994)
381-106091 Alaska (2014)
381-106093 C&NW (2014)
381-106095 Illinois Central (2014)
381-106097 Via Rail (2014)

4-car sets (Coach, Sleeper, Baggage, Dome)

381-106020 Undecorated (1994)
381-106021 Amtrak (1994)
381-106026 Baltimore & Ohio (1994)
381-106027 Burlington Northern (1994)
381-106028 Pennsylvania (1994)
381-106029 Southern Pacific (1994)
381-106105 Southern Pacific Set B1 (2002)
381-106106 Southern Pacific Set B2 (2002)
381-1061105 Southern Pacific Set B1 (2005)
381-106092 Alaska (2014)
381-106094 C&NW (2014)
381-106096 Illinois Central (2014)
381-106098 Via Rail (2014)

Single Cars

381-106002 Burlington Northern Baggage (2002)
381-106003 Burlington Northern Coach (2002)
381-106004 Burlington Northern Diner (2002)
381-106005 Burlington Northern Observation (2002)
381-106006 Burlington Northern Sleeper (2002)
381-106007 Burlington Northern RPO (2002)

2005 Union Pacific sets

381-1065011 Set A (2 Baggage Cars, "American Eagle" Sleeper, "American Beauty" Sleeper)
381-1065012 Set B (2 UP Coaches, Wabash Coach, C&NW Diner)
381-1065013 Set C (2 UP Domes, C&NW RPO, UP Observation)

2007 Great Northern cars

381-1061051 Set A (Sleeper, Dome, Diner, Observation)
381-1061052 Set B (RPO, Baggage, Coach, Diner)
381-1061053 Set C (Coach, Dome, 2 Sleepers)
381-1560701 Dome
381-1560702 Coach
381-1560703 Sleeper