The RailKing set was just an A-B-A. The Premier DAP set was an A-B-A plus an extra B-unit to make the A-B-B-A set that NS usually runs for that train. MTH used a special numbering system using the 20-8000X (the X being a different number each year) for the DAP program. It did not matter if the item was RailKing or otherwise. It got a 20- number. In 2009, MTH stopped that pattern and gave everything in the DAP program a normal item number that corresponded with the product line where it would have normally been offered. That means a 30- for RailKing, a 20- for Premier, a 11- for Lionel Corporation Tinplate, and so on.
Here are the Premier DAP item numbers:
20-80007B - NS F7 A-B-A w/PS2
20-80007C - NS F7 Non-Powered B-Unit
20-80007D - NS 5-Car 70' Streamlined Passenger Set
20-80007L - NS 70' Full Length Vista Dome
20-80007H - NS 70' Streamlined Sleeper/Sleeper Set
20-80007I - NS 70' Streamlined Sleeper/Sleeper Set