Very few sidecars are 'ambidextrous', as you put it, so its a case of replace about everything in sight.
Or the sidecar/chassis ends up facing backwards, and the door is inaccessible as well !
I chickened out on a sidecar deal after contemplating this...
Be aware too that Nortons redesigned their engines for 1948, with slightly more robust valve gear,
although for low use this may not make much difference.
With not huge power for overtaking fast traffic, the sidecar on the 'wrong' side may not make much difference. ?
We see you already have a 46 Model 18, so you already knew this ?!