Hi Scott,
As they were an Alfa Australia invention, the GTAM was the normal GT compliance plate with AM added on some cars, but not all depending on when , where or if they could be bothered perhaps! So far as I recall, only 1.8 was being made in RHD at that time so in order to run 2.0lt engine in touring cars racing here, they secured US 2.0lt Spica California emission engines (as they were the 2.0lt 116 engines in production at the time) and plonked them in 25 RHD bodies to come here. I'm not sure what the local tag of GTAM ever really had to do with the cars, other than reference the US emissions engine, all of which were eventually converted to carbs for the track anyway as the emission engine was hopeless. I remember going with Dad to road test one at Talbot Motors & its performance was awful compared to the 1.8 Sedan they also had available for test drives!
All these cars had the GT slatted C-pillar vent rather than the usual GTV item, as RHD GTV didn't exist (here) yet, so there is no reason to think that any markings other than a regular Alfetta GT would be on the shell.
Cheers,
Vin.