Will the grizzly carburetor fit on the 450 kodiak (2003)? And if so will it make much of a difference?
Trying to give the Kodiak a little more kick.

 

The griz carb is designed to work with 660cc and a 5 valve head, the kodiak works with a 2 valve head.
That really shows up in the carb specs...griz has a 42 mm carb bore and the kodiak has a 33 mm carb bore.
If you did find a way to make it fit, you would loose so much low end torque, due to the velocity drop of the air flow, youd hate it.
Have you looked into aftermarket pipes and jet kit?
Its gonna be a disappointment too...because according to this graph, there is at most a 1 hp gain using a jet kit,
graph for kodiak, finding and using a high quality pipe, may add another 1.5 hp.