Andrew,
 
I'm basing a lot of my assumption about the 1974 bullpen location on Tom House's catch of Hank Aaron's # 715 in the Braves' bullpen.  Here's a link to the Hall of Fame site's clip of that home run :
 
http://www.baseballhalloffame.org/media/player/mp_tpl.jsp?w=http%3A//mfile.akamai.com/31386/wmv/mlb.download.akamai.com/31386/open/moments/bbm_74reg_040874_ladatl_350.wmv&type=v_free&_mp=1
 
You can see several of the Braves' relievers beyond the left field fence where Aaron's hit went.  (I wonder if there's some possibility that the Braves moved the bullpen out there specially for Aaron's home run record season, of if the pitchers had gathered beyond the fence solely because Aaron was batting?)  My father may very well be right, though, about the bullpens being along the foul lines in the '60s.  In any event, a definitive answer to this will be interesting.
 
I thoroughly enjoy your ballpark site and greatly appreciate that you took the time to answer my question.
 
Thanks very much,
 
Steve Willoughby