Topic: 67 Running change -- Front Window to Vent window U-Channel

[Bossbill]

On the 67 front window to vent window U-Channel . . .

The MPC lists a C7ZZ-6521458-B | C7ZZ-6521459-B U-channel before 2/3/67.
It then lists a C7ZZ-6521458-C | C7ZZ-6521459-C after that date.

Not sure if this qualifies as a running change since I've never seen these U-channels side by side.

And, this is real close to my build date.
Anyone know the difference and if it's a visible difference?