Les, welcome to the Carrier forum of MLU.
I expect most of your questions can be answered to assist you with the restoration. Best wishes locating a Stacey towing attachment (if that is what you mean by "Leslie pintle hook"?). Late model N0-2 MKII* switch panels and dash lamps are a challenge, depending on your skills or the depth of your pockets.
Consider getting in touch with Brian Asbury in Southern Ontario (BCA on MLU) as he may have the marker lamps you are looking for. If you are stowing as Welsh Guards, the driver side lamp will be incorporated in the POW bracket. The gunner side has a separate bracket.
The large stowage box latches can be hand made, unless you can get Ben H. in England to make a set for you as a casting. Superb work and hard as Woodpecker lips when you want to drill them.
That awesome museum deserves an on-line look. I expect they could acquire a functional M10 Ross Rifle smoke discharger . . . you could spend some time on the smoke discharger thread and have a look at what Bruce P., Lynn E., Jordan B. and Ron P. as well as others have contributed.
There are a few different set-ups for the WS No. 19 in the MKII*, but perhaps the carrier you are working on has some clues to indicate how it was stowed?
How about some pictures of what you are up against?