As Herald says you've enough room to stick anything in there on a temporary basis from a salvaged unit or Hi Fi seperates to non-original period equivalents.
Of course you've got the case because the components are worth more separately and are likely to be hard to source-vandalism to most enthusiasts but then you may have saved the cabinet from destruction. Perhaps you could say more about what your really aiming at? You can get the "look" [with the lid closed] and play records to a good standard while you try to find the bits! If you want to use a decent valve amp [ie Quad 22] for example, that would not be cheap but very sell-able again for something more like the original. Youcan install the modern deck and perhaps mount some replacement spkrs on the original sites but have have you the skills there? There's lots of info on this site and more generally re the BD range.
Good luck with it i
.
Dave W
I did once make a posting about fitting a discrete modern amp intro an older case and would anyone spot that? Some people seemed a bit intrigued by the notion. If you were familiar with listening to BD's very possibly but not many people are!
These RG's are very sought after and admired but I notice other opinions to the effect that they were for the very rich and possibly built up to a price although I've no idea either way
Maybe you'll get some help [if you can do the work]. A chap on here is restoring a Vintage TV/Radio Unit which had the TV stripped out many years ago and people are finding bits and pieces.