Ok, it still confuses me as also the datasheet provided by Avago Techhnologies [2] states a pin order of Source (fat package pin), Drain, Source and Gate for pin 1, 2, 3 and 4. Note, the pin order in the datasheet is unusual, starting from pin number one and ongoing numbering clockwise (see also link [1] in my first response), usually the ongoing pin numbering is counterclockwise. Compare the pin order of your implemented spice model with those in the datasheet. Have a look at Fig. 11 in [3], there you also can see the pin assignment
Have you tried to rotate your ATF54143s 180°, so Gate and Drain pins are changed?
[2] **broken link removed**
[3] **broken link removed**
greets