FWIW, Garnett at C is still a bad fit next to Griffin.
Why?
Because what Blake Griffin really needs isn't a mobile defensive anchor with length to protect the rim, intelligence in guiding a defense, a willing interior passer, and jump shooting range for spacing.
Instead he needs is a.........wait a minute.......
He has all that-- not at garnett's level but still-- in Kenyon Martin and he's still a lousy defender and underdeveloped offensively.
What Garnett needs to succeed as a Center offensively is a another big who can stretch the floor so that when he does go into the post, the other team can't risk a double team. You can double way too easily off Griffin.
Kenyon Martin isn't any of those things, he's not a good jump shooter (despite his game 7), rebounder, or rim protector anymore. He's a scrappy bench big, no comparison.
Your thinking is completely inverted anyways if you had Blake Griffin and KG together you don't worry about Griffin impacting KG's offense, instead you use KG to
enhance Griffin who is a much more dynamic offensive player at this point in their respective careers.
Doubling KG is a losing proposition in the post anyways, he's too long,too willing a passer, and too skilled a passer for it to work for long stretches.