When I was HHC CDR 1-507th, I learned that the old regimental associations were a phenomonal source of info for anything or anyone even remotely associated with their regiments. Military guys are, for the most part, as big a group of
pack rats as teachers who never throw anything out because it may come in handy one day.
The "
11th Angels" was and remains a
'very tight' group. I'd contact their newsletter editor with your request and see what they could come up with - they'll have contacts which can come up with a lot of info and may even have a couple of guys who would remember your Dad. Somebody there may even know or have a contact for letting you know where he went after he left the 11th or they may have the info in their membership records/bios.
http://www.11airbornedivision.com/
I'd be pretty quick - they won't be around too much longer.
Gluck auf!
Richard