Charger trunk bracing.

[68hardchargerrt]

Hi folks,

Just wondering what the story with these trunk braces are?  Most chargers I've seen do not have these, but I have seen a few that do with various build dates thru the production year.  Anyone know why some have them and most others do not.  Also, I noticed that if it does have them, the deck lid has an open style bracing underneath as opposed to the more common solid bracing on the inside.  The silver deck lid picture shows the solid backed reinforcement, while the open one would be similar to the reinf. of the hood, open. 
The red charger pic shows the brace located next to the taillight bracket.  it runs from the trunk lip down to the bottom of the floor. 
Again,  the cars that I have seen that have this also have the open reinforcement on the underside of the deck lid while the cars without this brace seem to all be closed or solid.

See the difference in the back reinf. in these two:
http://s119.photobucket.com/albums/o142/chevellefan69/?action=view&current=IMG_4740.jpg
http://s119.photobucket.com/albums/o142/chevellefan69/?action=view&current=green68rt4spddecklidundersidepainte.jpg

Forget the arrow in the picture, but you can see the brace I described.  Don't have a pic of one without this brace.
http://s119.photobucket.com/albums/o142/chevellefan69/?action=view&current=68chargertrunkvalenceinsidearea.jpg

Anyone have any insight to this?

Thanks,
Greg.

[OttawaCharger]

Hey - my car is famous! 
Greg,
do a search for early model 68's.  They had a few differences which I can't recall right now but that is one of them.  as you've noticed, the trunk bracing and the trunk lid were different. My car (your last pic) was built in September of 67. 

[68hardchargerrt]

Thanks for responding.  However, one of the cars that I saw these braces on had a build date of 3-04-68 when mine has a build date of 12-08-67 and does not have these.  That's why I believe it might be a random thing.  I have seen various build dates with a mix of these features.

Just wondering if any of you guys know why and if you have them, what build dates?

Thanks,
Greg.