Yes, the Legacy Valk housing, with wiring, will work.
It is actually about 1/4" less diameter overall (per the pic), but it is about 1/4" wider, because of the allowance for the choke.
It looks more massive, because it is a lot more boxy looking. Although powder coating it black does help. It looks smaller in the picture because they are not the sa

It will however, need some trickery on the headlight switch. The Legacy Valk switch is low or high, make before break.
However, the 2014+ Valk LED light is low, and then low AND high. Would need a latching relay, or something similar, to hold the low beam power on when switched to high. It is doable.
It MIGHT be possible to trim the 2014 Valk headlight switch to fit in the Legacy Valk housing - in checking just now, it doesn't fit by slightly less than the amount the Legacy Valk turn signal switch did not fit the 2014 Valk housing...
Both means would also require some cutting/soldering/heatshrinking wiring.