Do all of the FWD Imprezas from the early 1990s have the hump to make room for the driveshaft and rear differential?

I am thinking of buying a FWD car sight unseen and want to be sure it will accept all of the AWD stuff from my donor car. Are there any FWD models that I need to avoid?

Nope, they all work for the AWD swap. IIRC, the 95 FWD Impreza comes with the AWD gas tank.