The potential issue for the car is that it may not be correctly registered. My car was "incorrectly registered" and I put it through the amnesty back in the day and managed to retain the age related plate and date of first registration. The description on the logbook changed from Lancia Beta Coupe to Hawk HF3000.
This car has continuous history from the 1980's in it's current form, carries the correct (donor) chassis number but didn't go through the amnesty and hasn't been through the SVA/IVA test. As such there is a risk to any prospective owner of a refusal of an MOT test (because it's not a Lancia Beta) but there is also a risk as the registration document doesn't disclose the correct engine number. So what's the result of any refusal? I suspect loss of the entitlement to the current registration and need to be presented for an IVA test in a form that it'll pass and will almost certainly end up with a "Q" plate. This might restrict it's saleability outside the UK depending on it's declared date of first registration? This is the worst case scenario I see. Which rarely comes to pass but for a sale outside the Uk with the need to satisfy local registration requirements I can't comment on. Hence Caveat Emptor!
Guy