1.On wikipedia:

456 GT: 1,548; 456 GTA: 403
Total: 1951

2.Type F116 Coupé from pininfarina produzione complesiva pdf:

Total: 1,435 (1992-1996)

3.From ferrarichat.com/ Ferrari Road Car Models and Production Numbers

456 GT and GTA
Production started: 1993.
Production ended: 1997.
Total production: 1,936 (402 auto); 202 RHD, 61 auto.
First serial number: 96244(?).
Last serial number: 111127(?).

http://www.ferrarichat.com/forum/ferrari-discussion-not-model-specific/196388-ferrari-road-car-models-production-numbers.html

4. From ferrari.com

factory type reference F 116 CL
chassis number road car sequence in the range 96157 to 111376,
production period spanned 1992 to 1998, during which time 1548 examples were produced

No info on GTA, M, or M GTA

http://www.ferrari.com/english/gt_sport%20cars/classiche/all_models/Pages/article_456_gt.aspx