Following the discussion above, Tony, I sense that the rev counter that I recall being fitted in my friend's 144 could well have replaced an earlier clock. The car was definitely fitted with the 'early' dash with a strip speedometer.
This would have been in the late eighties, and although they had the car for a very long time, I don't believe that they bought it new. All I can remember is that it looked 'factory', so if it was a modification it had been done very well.
I therefore do not see any practical reason why you could not do likewise if you should prefer a tacho to a clock.
Regards, John.