Is there any difference between 350z 2003 and 2006 rear brake calipers
 

is it?
I know the rear brake rotors are slightly bigger. Same thickness.
I am just not sure about the calipers.
I am trying to install dual calipers but it aint working.

Thank you.

They are not different. there is how ever dual and single piston caliper available for both model years

From a parts store employee, literally just looked this up for you