I have an 88 GTA that is in sad shape. I want to get the car repainted, but it has major body issues on 1 fender (mangled), and both quarter panels (1 mangled, both have rust).

I feel that it would be cheaper to replace the fenders and quarter panels before painting than the labor to have them repaired, especially since i'm not overly trusting of rust repair.

i'm looking for donor cars. so far i've found an 87 Firebird and a 91 GTA, both are the same color as my car.

my Q's are:
1) can the GTA GFX easily be installed on the Firebird body panels, or is it a major alignment issue or ordeal to drill the holes

2) can 91-92 body panels be used, or is it again an issue with the GFX holes lining up

 

Yes you can use a firebird fender for a replacement-I did, just had to drill hole for the GFX. I would suggest to use the earlier as they are more common and the front 91/92 style fillers are hard to find. The bumpers are one piece but the panels between can be swapped.
As far as rear quarters are concerned a pic would help but allot of work to change those.
It may not be worth fixing the car if it is rusty. Sorry if that is not what you want to hear.
I actually look for rust free rear quarters on a potential project car because it is really is what makes them worth saving. ( third gen birds are cheap and can be found very reasonable) If you really love the car it can be done but is expensive if you have to pay someone to do it for you.
I do all my own work and have done quarters on other cars but thirds can be found cheap enough that IMHO I would find a rust free car and put all the GTA parts on it.

Whatever you decide enjoy your car. (I know my wife loves her GTA)

 

now that i'm in TX, i am fully aware that it would be easier/cheaper to just buy a rust-free car and do an engine swap... but unfortunatley, I have a sentimental attachment to this particular car, so i gotta fix it up, regardless of the pain in doing so.

i dont have pics of the damage handy, but i'll try to take some