It's a Panther II chassis, and a Panther Ausf. G turrit.
This is the Panther II prototype with turrit:
The Panther II, would have alot of similarities with the Tiger II.
same tracks, transmission, suspension and roadwheels. while the dimensions were very similar to those of Panther Ausf G. Side armor protection was 60mm thick while frontal armor protection was 100mm thick.
" It was planned to arm Panther II with the latest 75mm KwK 42 L/100 or even 88mm KwK 43 L/71 (without muzzle break) gun mounted in newly designed narrow turret - Schmalturm (designed by Rheinmetall in 1944 and to be produced by Daimler-Benz)."
In the end it would be just as crappy slow as an Tiger II.