Depends on what you want the car for. If an everyday driver, the 351W is going to be a hard engine to beat if you want decent performance without driveability problems.
If the car is for racing, look at the requirements for whatever class you're planning to run. That said, there ain't no replacement for cubic displacement. If a weekend fun car only, the 460 will give you torque like there's no tomorrow. A small block can be built to give big numbers, but you're stressing what you've got, and have to pay close attention to the build. Several places (Ford among them) sell 460 crate motors, which would make it a drop in proposition, with a lot of hp and torque out of the box.
You mentioned the 390. Without disrespecting the 390, there aren't a lot of performance or aftermarket parts for the engine, which makes it a bit expensive and difficult to seriously build the motor. You're also getting all of the weight of the big block, without all of the displacement. If you want to do an FE, I'd try to go to the 428, as it will be easier to get power out of.
Carl