Horsepower difference

[ace59]

I'm looking to update my girlfriends sled, '01 550 fan, to a '03 500 classic with very low miles. Any idea how much more hp the liquid 500 might have? We rented her a 500 liquid cat last year for the day and she really liked it. thanks

 

[MARV1]

15hp if it is the standard Indy500 Fuji engine.