Merlin, here are the chords I used. Em sounds good to my ears, too, so I think you can go with your preference.
intro: [C Am F G] [C Am F G] [C Am F ]
If [G] I had a [C] hammer [ Am F ] I’d [G] hammer in the [C] morn[Am]ing [F]
I’d [G] hammer in the [C] even[Am]ing, [F] all [G] over this [G7] land
I’d hammer out [C] danger, I’d hammer out a [Am] warning
I’d hammer out [F] love be[C]tween my [F] brothers and my [C] sisters
[F] ah-[G] ahh, all over this [C] land [ Am F G ]
[C Am F G] [C Am F G] [C Am F]
If [G] I had a [C] bell, [ Am F ] I’d [G] ring it in the [C] morn[Am]ing [F]
I’d [G] ring it in the [C] eve[Am]ning, [F] all [G] over this [G7] land
I’d ring out [C] danger, I’d ring out a [Am] warning
I’d ring about the [F] love be[C]tween my [F] brothers and my [C] sisters
[F] ah-[G] ahh, all over this [C] land [ Am F G ]
[C Am F G] [C Am F G] [C Am F]
If [G] I had a [C] song, [ Am F ] I’d [G] sing it in the [C] morn[Am]ing [F]
I’d [G] sing it in the [C] eve[Am]ning, [F] all [G] over this [G7] land
I’d sing out [C] danger, I’d sing out a [Am] warning
I’d sing about the [F] love be[C]tween my [F] brothers and my [C] sisters
[F] ah-[G] ahh, all over this [C] land [ Am F G ]
[C Am F G] [C Am F G] [C Am F]
Now, [G] I’ve got a [C] ham[Am]mer, [F] and [G] I’ve got a [C] bell [ Am F ]
And [G] I’ve got a [C] song [Am] to [F] sing all [G] over this [G7] land
It’s the hammer of [C] justice, It’s the bell of [Am] freedom
It’s the song about [F] love be C]tween my [F] brothers and my [C] sisters
[F] ah-[G] ahh, all over this [C] land [ Am F G ]
[C Am F G] [C Am F G] [C Am F]