You don't want a locked diff unless you're only planning on driving in straight lines. When the car turns the outside wheels spin at a different rate than the inside wheels. Lock the diff and one will be skipping as it's not moving at the same rate as the other and you'll loose traction... in a turn... it's a crap move on anything but a "track only" car.
Go the distance and find a compatible LSD like all those folks before you.
