Y Duct revision

[139tech]

Question about the defroster Y duct on 69. Just pulled mine and it is part number 3949974. It is the original. My car is a 4th week March car and in the assembly manual GM introduced a new Y duct in March of 69 part number 3973729. My duct openings don't meet the dash cutout properly and am wondering if anyone has any insight into GM's March cut in 3729 duct. Was it a better fitting duct? Wondering if I should replace mine with it if that's the case. Thanks

[william]

There was a service bulletin on the change.

[139tech]

Fantastic, exactly what I needed! Thank you so much!

[john302]

Every duct we install they  never fit . They warp overtime and lose there shape . We gently warm them up with a heat gun and move it back in shape . Works great