Full Auto Sear Pack

Hey!

I am picking up a AA 89 pistol and wanted to know if I could purchase a full auto sear pack but not install it unless there was Marshall law or something crazy like that (like a Red Dawn situation, obviously I wouldn’t bother with the NFA at that point). Would I still need stamps and to fork out tons of cash other then for the sear pack if it was for this purpose?.

I talked to Atlantic Arms and they said that would be the only thing I would need to switch out in the gun to give it the full auto option.

Thanks!