Thanks for your answers. Actually, the AC identification tag shows identical numbers for the body and for the engine. Both is 1240. However, the original Ford engine had definitely a different much longer number. I don`t think that Ford used different number formats for the engines produced for the Mustang and for the AC Mk IV. Probably AC changed the original Ford production number into the AC engine number, and in my case this number has again been changed by the tuner.