Thunder at home are a no-vig 68.25% to win. Heat at home are a 62.26% no-vig to win.

So now that it's a best of 5, you get a table that looks like this, according to the books, assuming the lines don't change (much) from game to game, which they generally stay within a point(or 2) depending on who's at home (-5ish for Thunder at home, -4ish for the Heat at home)

Heat Thunder
Game3 62.26% 37.74%
Game4 62.26% 37.74%
Game5 62.26% 37.74%
Game6 31.75% 68.25%
Game7 31.75% 68.25%

So, doing a sim of 100,000 best of 5 game series', Heat win 50,140, Thunder win 49,860.

It doesn't get to be much more of a tossup than this. Heat odds to win -100.14; Thunder odds to win +100.86.

As I have the Heat rated (slightly) higher than the books think of them, this makes -103 on the series price a good bet.

Lastly of note, Bookmaker has -103 Heat/ -117 Thunder; 5 Dimes has -115 Heat/ -105 Thunder.

Good luck!