Hi Geoff
I've got a BM2400-2 open on my lab table right now, in for a complete restoration, so I took a look at what you're trying to do. Adding the missing components would be straightforward, except for the coils - no idea where to source those, except from a junker.
And then once you've installed the parts, you'd have to align the transmit/receive frequencies up. No small matter, if frequency counters and o'scopes are not part of your everyday equipment.
So, not a project I'd tackle, unless the customer was paying a lot of money, for what is essentially experimental work.
Menahem
Learn from the mistakes of others - you'll not live long enough to make them all yourself!