307 pistons are 3.875" diameter. 305 pistons are 3.736". It might be possible to bore a 305 large enough to accept the 307 pistons, but the wrist pin location would be .230" off because of the different stroke. In short, no.
I don't see why not,in my book a 350 is a good motor and will fit in i don't see why not,if they put 350's in a s-10 pick-up than it should fit in a nova,i have a nova it has a 307,i'm going to one day put a 350 in it,mines a 72 nova.