I'm pretty sure the harmonica is in the key of F.
Listen to the song for the pattern. 
He does some hammer on type stuff in the verses on the Am and into the F/C. 
The last lines of each chorus are just F and G then back into the verse chords.
Standard tuning. 
F/C=an F chord with a C bass note. 
Any questions email me at digitaltlj@hotmail.com


Am  F  C  G  x2

Verse 1: Am  F  C  G
Old man are you tired
Will I one day fill those boots
Walk the world over
In search of righteous truth
Old man are you gone
Down to the proving ground
Sir your time is served
Now let me make my rounds

Chorus: F  C  G  Am
For my cause I'm a walking down for my judgement day
For my land I'm a coming round to pay what you have paid  
With my hands I will dig and build and bleed until I lay                
Then wash my feet in the waves

Am  F  C  G 

Verse 2: Am  F  C  G
It's high time to carry on
And march to my own drum
Kick the dust up son
And wear the soles down some
It's high time to carry on
Horizon on the run
Walk the world over
And know I'm not alone

Chorus: F  C  G  Am
For my cause I'm a walking down for my judgement day
For my land I'm a coming round to pay what you have paid
With my hands I will dig and build and bleed until I lay
Then wash my feet in the waves

A  F  C  G

F  C  G  Am  x3

F  G

Chorus: F  C  G  Am
For my cause I'm a walking down for my judgement day
For my land I'm a coming round to pay what you have paid
With my hands I will dig and build and bleed until I lay
Then wash my feet in the waves
Then wash my feet in the waves

Am  F  C  G  x2

End on Am