I'm sure the 2013 Heat would lose in a 7 game series to all of the following:
2009 and 2010 Lakers - They kill the Heat on boards and get enough offense from Kobe
2008 Celtics - Doc Rivers, and Tom Thibodeau would have found a way shut the Heat down. The 08 Celtics had alot of front court depth and would have had the rebounding edge.
2007 Spurs - Bruce Bown was the Lebron stopper
They would probably get swept by the 2005 and the 2003 Spurs as the Spurs were the best defensive team in the league in those days and if the Heat had no answer for Roy Hibbert they would certainly have no answer for Tim Duncan back when he was an MVP
2004 Pistons because their defense
They would be swept by the 2000, 2001, and 2002 Lakers as they would have not answer for Shaq. By the time the playoffs came around Shaq would finally be in shape and I don't think the Heat could stop him from get 40 points and 15 boards on a nightly basis.
1999 Spurs - David Robinson was still then so they would have both Duncan and Robinson killing them on the board
1996, 1997, 1998 Bulls - Scottie Pippen in the 90s is probably the ideal person you would want to guard Lebron.
1994, and 1995 - Hakeem kill the Heat inside, for the record I think with there defense and physical play the 1993 and 1994 Knicks would have been a problem for Miami
1991, 1992, 1993 - I these groups didn't have the regular season record of the 1996 Bulls but I feel that these Bulls were probably the best of the Bulls. Especially in 1991/1992 when Cartwright was still a fairly high level center. Horace Grant was a high level athletic 6-10 guy with long arms perferct guy to defend Chris Bosh. Then you had Pippen and Jordan at his very best.
I could go back further but I'll stop right there. So basically the only champion the 2013 Heat might have defeated in my opinion was the 2012 and 2006 Heat.
