74 Duster Question

I need another project like I need a hole in my head. But this car peaked my interest. Near where I live a guy has a 74 Duster with a slant 6 and a 3 on the floor for sale. Back in the day I had a 72 with 318 and 3 on the tree. My Question, is this fairly rare to have a 3 on the floor? Can't say as I have seen one.
I have only seen pics of the car and not seen a fender tag. So I'm hoping you helpful people could school me a bit.
Thanks in advance.