Depends on what you mean by bolt up. I am not aware of anyone trying to fit an AWD fuel tank without adapting the car to AWD itself.
Their shapes are pretty different. The gas tank straps should fit into the same location. You will also have to plumb the spare lines, as the AWD tank has a subsender, where your FWD model does not. Being that your car is OBDI should make things easier with regards to emission lines.
Judging by the fuel tank swaps I've done in the past, I'm going to suggest you source a FWD tank or go with an AWD conversion. The tank's are really jammed up in there with almost no room to spare as it seems Subaru wanted all the capacity they could get. I imagine the rear suspension differences and fuel tank shapes would make this challenging to fit.
This is an older diagram for 1990-94 Legacy's but it shows their general shape side by side.
