2008 xl heater

[Doubeleive]

Doubeleive, I found one for sale like the picture I posted here and it appears to be like your right picture but with the long cooling (?) duct missing. Does that make sense?
It is the part number that GM parts sites list for mine but mine has the short duct like your left picture.
Would the right one on your pictures would properly without the cooling dict?

You might be able to transfer the cooling duct over from your old one not sure