Is it a real (as in on paper) proposal? 
Yes, a real project but no prototype (or mock-up AFAIK). The final variation had an up-armoured turret much like the Leopard 2A5. A rough translation:
"TAP (Tanque Argentino Pesado)
In the middle of the '80s, TAMSE began development of a TAM successor of the TAM for the '90s, the Tanque Argentino Pesado (Heavy Argentine Tank). TAP would incorporate 65% TAM components but would be better protected, have improved electronics, and a 120mm Reinmetall L/44 gun. TAP would have a lengthened chassis (with seven roadwheels instead of six) and a more powerful, domestically-produced engine if possible.
TAP would weigh in the order of the 51.5 tons. Despite the economic problems of the '80s, the TAP project advanced well. Unfortunately for TAMSE, the Exército Argentino showed no interest in TAP. TAMSE looked abroad for clients and Iran was interested (along with TAM and VCTP) but export permission was not granted. With no expectations of production, TAMSE then abandoned the TAP project."
Re: that
Dragon SPAAG, does anyone know for certain what 30mm guns TAMSE was proposing?