Dan Fogelberg does this with open G tuning of some kind, but I can't figure that out, but here are some chords that fit well, and can be capo'ed to fit most vocal ranges. Intro: One verse instrumental

^CLonger ^Dmthan there have been ^Emfishes in the ^Focean ^CHigher ^Dmthan any ^Embird ever ^Fflew ^CLonger ^Dmthan there've been ^Emstars up in the ^Fheavens D# Dm C F G(bar'ed) I've been in love with you

^CStronger ^Dmthan any ^Emmountain cath^Fedral ^CTruer ^Dmthan any ^Emtree ever ^Fgrew ^CDeeper ^Dmthan any ^Emforest prim^Feval ^D#I am in ^Dmlove with ^Cyou

^BbI'll b^Fring ^G#fire in the ^D#winter ^BbYou'll s^Fend s^G#howers in the s^D#pring ^BbWe'll f^Fly t^G#hrough the falls and s^D#ummers With l^Gove on our w^G7ings

^CThrough the ^Dmyears as the ^Emfire starts to m^Fellow ^CBurning l^Dmines in the b^Emook of our l^Fives Though the ^Cbinding c^Dmracks, and the ^Empages start to y^Fellow

^D#I'll be in ^Dmlove with ^Cyou ^D#I'll be in ^Dmlove with ^Cyou

D# Dm C F - G

^CLonger ^Dmthan there have been ^Emfishes in the ^Focean ^CHigher ^Dmthan any ^Embird ever ^Fflew ^CLonger ^Dmthan there've been ^Emstars up in the ^Fheavens ^D#I've been in ^Dmlove with ^Cyou

^D#I am in ^Dmlove with yo^Cu D# Dm C

Dan Fogelberg - Longer