IF you're trying to cool dowm the interior part,and thats quite simple and easy.
All you need to do is to make an intake and exhaust.

1-You can put up to three intake fans on top IF you're planning to make your case to inverted BTX.Which means your power supply will go down at the bottom part of the case where it will not blocked the three fans on top.

2-You can put two intake fans on top IF you're planning to make a simple ATX where your power supply will stay on top BUT i will not blocked your fans space because you're using only two fans instead of three.

3-You can make a extra 120MM intake in front panel.

4-You can put a 120MM for exhaust at the rear parts where hot air will come out of the case.

5-You can also make a 2 X 120MM for exhaust at the bottom part of your case.

-Good luck-