When I tried to find information about whether the F-104S.ASA had 6 x AIM-9L, I found that there could be 3 missiles on one wing, 2 under it and one on the end and there were non on the underbelly. “Up to two Sparrow; and two, theoretically four or six, Sidewinder missiles were carried on all the hardpoints except the central (underbelly)”
F-104S.ASA has the same hardpoints so give it 6 Aim-9L
Well in war thunder things don’t have to be perfectly historical, so I see it possible that gaijin could let the F-104S use sparrows on the two empty hardpoints possible, and without removing gun just to make it more balanced