I know that the 350 and 455 are the same,so if the 350 will fit the 340....There's a high torque starter,but that one will fit both.Bruno.
350 and 455 starters will bolt up to each other but I recall the 455 unit has extra windings for the additional torque need to spin the larger engine. You can see the additional copper strap on the back of the 455 unit.