Odds of flopping a straight draw

I am trying to figure out how to calculate the odds of:
-flopping an open end straight draw or double belly buster straight draw
-gut shot straight draw

with starting hands of:
-0 gap connectors (w/ maximum stretch)
-1 gap connectors (w/ maximum stretch)
-2 gap connectors (w/ maximum stretch)
-3 gap connectors (w/ maximum stretch)

Obviously an open end or DBB straight draw isn't possible with a starting hand with 3 gaps, but other than that I am having difficulty coming up with a solution.

Can anyone point me in the right direction here?