Did you see the ending to the movie "Deep Throat"? Why would you want something smaller unless there was a cost issue? Torque is king on the street, max RPM is a rare item. IF you can find a 400 that is in good shape to rebuild, the parts cost is comparable to the 350...... think of it, if you had a 300 cubic inch
engine and someone would offer you 50 cubes for the same price, would you take it? darn sure you would

Put the 305 valve covers on it and pretend it's a 305!!!