Martin. Additional detail concerning my earlier recommendations. It depends if you just want something that works, or true original parts to suit the model year.
Airbox and filter element changed over time.
1947 Rigid frame Longstroke A7 Engine Air box battery carrier 67-4535, Filter 67-4545. Connecting hose 67-4546
The connecting hose is straight and faces forwards towards the carb. Hole in airbox faces forwards.
1947/48 appear to be the same basic parts.
1949 Rigid Frame to ZA7 109 Airbox 67-4535 Filter 67-4545 ( 2 screw Fixing)
Rigid Frame ZA7 110 onward Airbox 67-4558 Filter 67-4562 (3 Screw Fixing)
Plunger...Same as Rigid ZA7110 on. Airbox 67 -4558 Filter 67-4562.
1949 models continue with the straight coupler 67-4546, from 1947. Airbox hole still faces forwards.
The filter units look to be the same basic profile, detail difference being just the number of retaining screws.
Can't tell if there is any significant difference, other than the number of screws but chewing this over makes me think your original airbox could be made to work.
If the bike is a 1951 A7 Plunger, then the correct airbox with the outlet facing the oil tank is the one you want, which was introduced for the A10 in 1950. This is the airbox and filter we are more familiar with, requiring the rubber elbow hose.
Airbox 67-4594 Filter 67-4600 (3 Screw Fixing) Connector Hose A7 67-4596 A10 67-4589
Fitted to Plunger Frames, also possibly to Rigids, the catalogues are somewhat vague at this changeover point.
Nourish, All of the above gleaned by reference to Parts Catalogues, so apologies for not researching deeply enough previously before posting. Some of these variations were new to me.
The answer to your question isn't here, but we can see some variations exist, position of air hose, screws securing filter element and possible variations in the profile of the pressing for the airbox.
Errors and omissions? Someone check my part numbers please, I need a lie down!
Swarfy.
