No idea on what carb they had, it was just a guess. I could have sworn I had a 75 or 76 Duster I used for parts back in 91 or so that I thought was a 360 2bbl, but it was a lot of years ago so who knows. What I did find recently does support the point that they were all 4bbl's, though.
If '75 was the year they mandated catalytic converters on cars, wouldn't that kind of force the dual exhaust to go away? Not certain where or when, maybe '75 was only for parts of the US (like California), but I thought it was nation wide. If so, pretty sure it would require a single exhaust.
