My experience with National has been:

Ford - Almost always fully loaded or close to it
Chevy - Almost always LT, occasionally Premier
Nissan - Almost always SL or higher
Kia/Hyundai - Always base trim
Chrysler - 300 and Pacifica only, which come well equipped even at base trim
Dodge - Not many but they vary
Jeep - Usually Limited, occasionally base
Toyota - Almost always base
Mazda - Midlevel
Volkswagen - Jettas are base, Atlas are midlevel
GMC - Usually SLT