Jon, yes, I was intending to put the number on a new plate, just for completeness but I will now wait to see if you have any luck when you can access the Register.
Some details of the car are fairly certain; there is the body number stamped on the top of the tunnel, and old chassis plate on the scuttle, the reg. number is the original and it even has the suppliers plate on the dash. The engine Number is for a second hand replacement from the Dorset club at a cost of £3 10s 00, remember this was a LOOOONG time ago and it doesn't really affect what remains of the car. I don't think that anyone would be fooled by a shiny new plate but I don't mind amending the register to show this fact.
Brian

Location: Near M1 Motorway Jtn 28

Hi Brian. If you know the chassis number, it should be possible using the Register to narrow the car number down very precisely, if not exactly.

Edit: Ha! Dave's beaten me to it!

Location: Herefordshire, with an "E" not a "T".

Brian - Dave and Dave have already assessed I'm sure - I was just meaning that if there is the slightest chance it could down to one OR the other, then you can't quite be exactly sure... !

Sorry I haven't accessed the A7CA register, I was working from the RN register that is on my computer.

As it doesn't look as though I can get any near to finding the real car number for my RN, I have decided to stamp the plate with "B4 70XX" to avoid any confusion (or perhaps to cause even more!!)
Brian

Location: Near M1 Jcn 28

Your approach is far more honest Brian, if you document this on the cars paper work future owners will be under no illusion. To illustrate the problem we have a car here in NZ with almost certainly original identity plates and yet there is a car in the UK claiming the same number.

Location: NZ

Thanks for the suggestion JonE, sounds like a good idea.
Brian

Location: Near M1 Motorway Jtn 28