Damn, that's right. My bad.
What you can do then, I don't know if this is the best way around it, but whatever.
Open up atlac85a.viv with
BigGUI and export atlac85a.fsh. Then open it that with
FshX and export the jersey texture.
Do the same thing with atlaaway.viv, but instead of extracting the jersey texture from atlaaway.fsh, import the retro jersey texture instead and save it. Then put the updated atlaaway.fsh in the \SGSM\ folder.
That method only replaces the jersey texture, not the numbers. If you want those as well, then open the atlac85a.viv and export the atlac85a_num.fsh and rename it to atlaaway_num.fsh and put that in the \SGSM\ folder. Do the same with the other two files in the .viv file (*_nreg and *_size).
This doesn’t get the name on the back of the jersey over though, and I have no idea how to get those to work.
There could very well be an easier way of doing this, but this is the method I could recall at the moment. Hope it'll do for you.