Note-for-Note - Transposing 2nd Position to 3rd Position

And now for 3rd Position. Play the Rhumba rhythm again over the 12 Bar Blues Progression in 2nd Position.

C Harmonica in 2nd Position (Key of G)
I = G B D = 2 3 4
IV = C E G = 1+ 2+ 3+
V = D F# A = 1 2' 3"

Now grab your Low-F Harmonica and play the same notes in 3rd Position:
I = G Bb D = 4 5 6
IV = C E G = 6+ 7 8
V = D F A = 6 7+ 8

You'll notice that by trying to retain the same pitch range that the I and V Chords are minor. To perform major chords you'll need to move this version down an octave. We can do this on the Low-F, or grab the standard F (the highest standard harmonica) and we luckily retain the same pitches, but in their major form.

I = G B D = 1 2' 3"
IV = C E G = 2 3 4
V = D F# A = 3" 4' 5+

You may say, "Man, those bends look tough to play and even harder to make sound good." and you're right, but that I chord note combination is used all the time by experienced harp players, so get to work. The major form of the V Chord is uncommon, so a simple substitution is in order. Most players will play a 2+/5+ octave for the V Chord and then improvise over the IV chord to get back to the I.