According to the Ford web site vehicle configurator, the E-450 has a 4.56 axle and the E-350 can be ordered with either a 4.10 or a 4.56 axle. Both come in limited-slip and non-limited-slip variants.
A bigger number for the axle ratio means higher engine speed for the same wheel speed (assuming, of course, the transmission is in the same gear). I understand that a bigger number is usually called a "lower" ratio (in the same way that a lower gear in a transmission has a greater reduction than a higher gear). This is indeed somewhat confusing.