Big block or small block
if the duster is a factory 4 speed car and a v8 car originaly you will need a big block bell crank at least to switch over,,if you already have headers for the small block and other items as such you are going to need all those to fit the big block,,so if money is no object,,its pretty much your choice,,it wll be nose heavy with a big block with iron heads for sure,,but will put ur butt in the seat when u stomp on it,,,
all depends on what you plan to do with this car and your budget good luck
