? re 40 v 357sig mags

I own beau coup Glock 9's and am thinking of buying a buddies G35 it has 2 40 mags and 5 357 Sig mags.

I realize the 357 is a necked down 40 , I know you can interchange the 2 mags.

my questions is although the body is the same is the spring and follower the same?? If I get this should I swap the followers out or are they the same??

PLEASE no opinions, please only if you know for sure....THANKS.