The Mark 3 was always my favourite of the big Fords, it was the first car that I remember being introduced (I was five when they came out ) and my first car was a Mk3 Zephyr 4.
There are 3or 4 on the market at the moment all under 5,000 and all not sold.
It seems that the only ones to make good money are the really clean original models and even then top money is around £8,000.