As I understand, you're trying to locate individuals who may have known and/or served with your father. 260th Infantry was an organic element of 65th Infantry Division. Company F was an element of the regiment's 2d Battalion - one of the battalion's three rifle companies.
I have two addresses for the division's veterans association:
65th Infantry Division Association c/o Fred Cassata 123 Dorchester Road Buffalo, New York 14213-1444 (Fred assisted me in researching the division's only Medal of Honor winner a while back)
Perhaps they can assist in locating individuals who remember your Dad.
You might also want to ask about the 260th's regimental veterans association (address, whether still active, etc.). It's important you specify you're seeking former members of Company F and/or 2d Battalion (other elements of the battalion were attached to Company F from time to time).
(Coincidentally, the Medal of Honor winner referred to above was killed while treating wounded under fire during the action at Saarlautern.)