Firewall AC Box--Color/Year application ?

Which box is used in which year(s)? I have what I refer to as a "brown" box as well as "grey" box. I know GM changed the colors at some point but don't recall when. Anyone???

My 72 has the "brown" colored box.

Thnx, Patton

this thread has a pic of both:

http://v8buick.com/showthread.php?t=86462

 

I think 72 is brown.

 

My 72 is brown also!

 

My 69 GS400 convert is brown

 

thnx guys. Patton

 

Grey Box

I have a 72 Suncoupe with factory air and it has the grey box.

 

I am working on a 72 Skylark with the grey box. Feb build date.