I just discovered this song a few days ago and I really liked it.
I haven't heard the actual mp3 version so this tab will be based on Sam Harts 
performance on Youtube.

Standard tuning
Capo on 3rd fred
Tabbed by NMahler

Intro, verse and chorus

C                            G                                  
--0-0-----0-0-----0-0---0-0-|--0-0---0-0---0-0---0-0-|
--1-1-----1-1-----1-1---1-1-|--1-1---1-1---1-1---3-3-|
--0-------0-------0-----0---|--0-----0-----0-----0---|
------0h2-----0h2-----------|--0-----0-----0-----0---|
3---------------------3-----|------------------------|
----------------------------|3-----3-----3-----3-----|

Am                       F      
--0-0---0-0---0-0---0-0-|--0-0---0-0---0-0---0-0-|
--1-1---1-1---1-1---1-1-|--1-1---1-1---1-1---1-1-|
--2-----2-----2-----2---|--2-----2-----2-----2---|
--2-----2-----2-----2---|--3-----3-----3-----3---|
0-----0-----0-----0-----|3-----3-----3-----3-----|
------------------------|------------------------|


Bridge

Em                       F
--0-0---0-0---0-0---0-0-|--0-0---0-0---0-0---0-0-|
--0-0---0-0---0-0---0-0-|--1-1---1-1---1-1---1-1-|
--0-----0-----0-----0---|--2-----2-----2-----2---|
--2-----2-----2-----2---|--3-----3-----3-----3---|
------------------------|3-----3-----3-----3-----|
0-----0-----0-----0-----|------------------------|





Links

Mario Kart Love Song on Youtube:
http://www.youtube.com/watch?v=VDBpQVhCMb8&feature=channel_page

Sam Hart's Youtube account:
http://www.youtube.com/user/blinktwice4y

Where to buy his music:
http://www.cdbaby.com/samhart