The original aluminium is indeed 2024 .032 for your year. I am replacing mine now and have gone over to 5052 .025. The 2024 does not flex and bend as easy so I used the 5052 instead. If you do use 2024 bend it slowly and gently for it will snap on the bend if it is too sharp. If you are doing a shell on replacement, getting the new up in between the skin and then making it bend in literally three directions can be a challenge. My first attempt ended in a wasted sheet that looked like someone had trampled it. I am not claiming to be an expert now, just passing on what I have learned the hard way. When you put it on, finesse it, do not use force. I found it almost needs to be massaged into place. I wish I had better photos on my blog to show how it was done, but it is hard to do something that requires seven hands and be able to operate the camera at the same time. A competent willing helper is definitely needed in my opinion to do this job.
Also, an excellent source for aluminium is Airparts Inc. Homepage
They have everything you need from sheet and coil aluminium to clecos to rivets. The service is excellent, being a family owned and operated business. I cannot recommend them more. I personally hope you purchase from them. They can also answer any questions you might have, for not only do the supply many plane builders, but they supply a lot of Airstream restorers.
One thing they do not have is #5 or 5/32 sized solid rivets, Chris said they will be stocking the right ones soon due to the high demand coming from us Airstreamers.