thats not a weapon its a Weapons rack - they dont appear in the loadout screen
That code is more about limiting what weapons go on a station and only applies if you want to put on a weapon that has been given a specific code - you wont find many jets have this - look at the F-4D_67:
[FalconStation1]
SystemType=WEAPON_STATION
StationID=17
StationGroupID=2
StationType=EXTERNAL
AttachmentPosition=-2.32,2.59,-1.17
AttachmentAngles=0.0,-1.0,90.0
LoadLimit=90.72
AllowedWeaponClass=IRM
AttachmentType=USAF
ModelNodeName=missile_rails_L
PylonMass=
LaunchRailNodeName=
SpecificStationCode=AIM4
Because it has the code AIM-4 only weapons with the code AIM4 will go on that station - thats it
if you look in your weapons editor at the AIM-4D it has a code of AIM4 - similarly you can set the AIM-4A/B/C to all have the specific code AIM4
Heres another weapons rack btw so you can see
[WeaponData001]
TypeName=BRU3A
FullName=BRU-3/A Ejector Rack
ModelName=BRU3A
Mass=105.500000
Diameter=0.000000
Length=4.393000
SubsonicDragCoeff=0.200000
SupersonicDragCoeff=0.770000
AttachmentType=USAF,UK
SpecificStationCode=
NationName=USAF
StartYear=1955
EndYear=2020
Availability=3
BaseQuantity=21
Exported=TRUE
ExportStartYear=1955
ExportEndYear=2020
ExportAvailability=0
WeaponDataType=6
WeaponsRackType=MER
NumWeapons=6
LoadLimit=500.000000
LengthLimit=2.000000
MaxFuelAmount=0.000000
Attachment01Position=0.160000,1.366000,-0.160000
Attachment01Angle=0.000000,0.000000,-2578.310078
Attachment02Position=0.160000,-1.366000,-0.160000
Attachment02Angle=0.000000,0.000000,-2578.310078
Attachment03Position=-0.160000,1.366000,-0.160000
Attachment03Angle=0.000000,0.000000,2578.310078
Attachment04Position=-0.160000,-1.366000,-0.160000
Attachment04Angle=0.000000,0.000000,2578.310078
Attachment05Position=0.000000,1.366000,-0.423000
Attachment05Angle=0.000000,0.000000,0.000000
Attachment06Position=0.000000,-1.366000,-0.423000
Attachment06Angle=0.000000,0.000000,0.00000