I have a 383 in my dart. Cold case 2 row radiator, flex fan, and a shroud. On a hot summer night in Phoenix, sitting at a light, it might get to 195*. Driving it runs at 180* (thermostat temp) all day long.
Yes, 12x12. The shop itself is basically 60' across the front, and 50' deep. I wanted to go taller, but the city wouldn't let me. It fits all my junk, with a little room to spare.