Would my Duster run cooler with an electric puller fan?

If you're running an original 22" radiator with the upper radiator hose on the driver side & lower hose on the passenger side, the 2998325 should be correct for your 340 Duster.

Here's a picture of the hood to radiator seal mentioned above which I would also recommend installing...

Thank you. My hoses are as you describe. I think I will order both items.
I'm not very mechanically inclined... it seems the fan must be removed to install shroud? I'm old (69) but not very experienced in car repairs.