Sb/bb?
I have a 360, so I really like the smallblock choice(it sure rev's nice). But when I blow up this engine, I really want to put in a BB. I already have an extra one taking up space that would fit nice, so thats my future plan. I have no idea how it will handle with a BB in my Duster, but I do know its a big engine with lots a torque in a small mopar. To me, that would put a BIG smile on my face.
I think with the tubular K-Frame/suspension route that you mentioned, a BB would handle pretty good (and the right torsion bars). I guess on the downside, plugs are easier to change on a SB, but the oil filter is easier (at least for me) to change on a BB. A 383/400 is going to fit the best of the BB engines, and it is 65lbs lighter than a 440. Whatever you choose, its going to be fun!