Yes, you can use it for GAF. Do you have a Moisin Nagant to pair it up with?
I have no experience loading it, but I have read something about loading it, I think on surplusrifleforum. Seems that they are a bit challenging. If I remember correctly, the Lee dies are designed to use 32-20 cases, but if you find some proper cases, not so well-they were using a 30 carbine sizing die for those, I think. You might also search on Castboolits website, they discuss loading all sorts of old oddballs over there.