Thanks, guys, for the help!

So, looking at this closer, it has the smaller radiator opening, not one for a 26" radiator. No skid plate, no torque boxes, and the rear springs are stock-style (non-SS). There is a rear seat with the car, but there's no sheet, the glove box is missing, and little remains of the interior, including carpeting, headliner, and the gauge cluster. I'll clean the housing for numbers on the Dana Monday. Why it has a Dana, no idea but someone most likely added it, although there are no performance mods (better springs, tied frame, no evidence of even the obligatory 'slapper bars.') So, we're thinking it's just a 383 car with a swapped-in Dana from way back when these were in junk yards.

The green 383 car, though, has the 26" radiator opening and SS-style rear springs.