70 and 71 E-bodies had the 8K tach, while the later years had the 7K. Although it has been said a few leftover 8K tachs might have been put into 1972 cars. I can't help with your production numbers question, but I sure someone else will know.
Mike
My '72 has the 8K tach from the factory. It was an early '72, made 8/17/71.
What production #s are you looking for?
All 'Cudas and Challengers from '70-74 or a particular year?