Not for lining up unfortunately, the tail shaft is toast

that's had quite a knock to break the splines and, it may be just the angle of the picture, the shaft looks bent as it sits to one side of the seal lip. If it's not bent then you might get away with it but it's a risk.
It is an Arrows series box so not a straight swap, the bell housing/input shaft is longer than the Commer one and the casing is canted over for the Hunter type engine installation. It can be fitted to the Commer engine by fitting the Commer internals onto the O/D mainshaft so the shorter Commer input shaft and bell housing are used, the Commer layshaft must also be fitted.
You can't mix and match the gears as the Commer and O/D have different gear ratios.