1979 GMC K2500 body work questions

[Zigy]

Hi, I have a couple of stupid questions for you all.
I pulled my windshield and have found some hidden secrets
I have some rust going on in the windshield channel.
I will try to add some pics so you can see exactly what I'm talking about.
I will need to replace two spots. Passenger side top and driver side bottom.
My questions are:
Can I order after market panels to fix this and if so what are the panels called?
If I can't and need to cut up a scrap cab for my patches. I'm wondering what cabs are compatible. Is it 73-80 or 73-87?
Is there any difference between chevy and gmc cabs? Also is there a difference between a 1/2 and a 3/4 ton cab?
Thank you so much for your help in advance

Ps
I don't know why I can only upload one pic a post or why they are rotated sorry.

[Zigy]

This is passenger top post sorry it's rotated again lolAttachment 1512163[/ATTACH]

[chrismoore701]

This is the link to my build

http://m.imgur.com/a/bURrE

Look down about 1/3 and you will see what I did. Go to the junk yard and cut out more than what you need. Cut out the spot welds and you have a patch. Pretty sure all cabs are the same. 73-87. Double check and good luck

[Chknlyps2]

Windshield & rubber are the same for 73 to 87 on Chevy and GMC 1/2 ton to 1 ton and I think the larger 50 & 60 series are the same rubber and glass also so the cab metal around the opening should all be the same.

[Zigy]

Thank you for the quick replies guys!
Chrismoore701 I think I'll end up doing the patch work that you suggested.
I can't check out your link. For what ever reason I click on
Download remaining 141 pics and nothing happens.
Chknlylyps2 hahaha love the name lol
You truly think out side the box. I never would have thought to check the rubber and glass sizes. Great idea and thank you so much!