Ok, just found some info:
"There are five different cars & different Aerosmith tracks play in each; each car also has a unique number plate, shown below in brackets -
1. Nine Lives (1QKLIMO)
2. Sweet Emotion (UGOGIRL)
3. Back in the Saddle & Dude Looks Like a Lady (BUHBYE)
4. Love in an Elevator & Walk This Way (2FAST4U)
5. Young Lust, F.I.N.E. & "Love In A Roller Coaster" (H8TRFFC)"
From:
http://www.wdisneyw.co.uk/atrnr.html