There are 2 versions of this control unit.
Early - 191919376 - marked 43
Late - 191919376A - Marked 42
The early unit (43) operates slightly differently under a low coolant condition where it will cause the temperate gauge need to read maximum (overheat)
The later version (42) works a little nicer and continues to give a relaible temperature gauge reading regardless if you have a low coolant condition or not Flashing red temperature light)
These control units are interchangeable so this unit will fit in place of a 43 and can be considered an upgrade.