
I haven't tried it, and wouldn't recommend it, but I suppose with a bit of ingenuity you
could - but probably shouldn't... You would need a complete slide/barrel in .45 for starters. There's no way you could use the GSG slide for the purpose. Then you would need to do a bit of work to fit a proper ejector to the frame of the GSG. You will also need some mags in .45 ACP. The GSG frame will take the mags, and the slide stop pin should probably line up ok with the barrel link...
BUT that gun is not designed to take the abuse of firing .45ACP ammo. I don't know how many rounds you could get off before serious problems start to develop.
The GSG was designed from the ground up as a purpose-built .22 LR gun that would take most aftermarket 1911 parts to improve ergonomics and function for shooters... It was never designed to take a center-fire conversion kit.