Upper defroster vents- 84 911

[Jon Hile]

is there any significant difference between the upper left and right defroster vents for an early 911 (up to 1977) than the 84?

Looking at the diagrams they appear to be very, very similar.
The reason I ask is mine are warping slightly (sun damage no doubt) and needing replacement. The cost difference is significant (like $5.00 each for the early 911 parts versus $23.00 each for the 84!).

I'm sure I'll end up having to spend the higher amount but wonder if anyone has any experience with these...