1933 16h

Hi David,

   I have not seen your gearbox, but I guess it is a WD 16H. All these gearboxes use the same fixing, so there should not be a problem. The 1933 2 main bearing engine uses an engine mounted shock absorber whereas the later shock absorber is in the clutch. You can use both of these together, but if you have not got the engine s/a you will need a sprocket with the off-set on the outer side for the correct chain alignment.

Good comments above but if you're hoping for originality the dolls head gearbox wasn't available till 1934.
If that doesn't bother you it can be made to work with correct alignment of sprockets easily enough. 

Internals can be swapped, but TNS has been reported on SWD WD Big 4 boxes. Standard boxes are marked "NS" 'Norton Standard" ? TNS might be Trials as it was a wide-ratio box with a very low 1st...Have a look at the pinions anyway.