I think the difference with juice is about 15-20%. Lets say he started juicing in 2000, since thats when his numbers really jumped. He hit 258 2000-2004 then was hurt most of last year. Subtract 15% from 258 and you're still left with 219 so even with that scenario he'd be at 676 naturally.
Year Homers
1990 33
1991 25
1992 34
1993 46
1994 37
1995 33
1996 42
1997 40
1998 37
1999 34
2000 49
2001 73
2002 46
2003 45
2004 45
2005 5