Need some opinions
Welcome
@clogsmith !!! I see you find yourself in a bit of a pickle. As you can see I to have a car of the same vintage of yours, but the '75 Duster version. Mine was not inherited from an estranged family member though; I inherited another guy's problems and paid him for them.
As far as your "What to do" list for this vehicle, I'm going with
Option #4. This whole endeavor started with the sale of an '89 Yamaha V-maxx w/ a blown engine for $900 6 yrs ago. Flipped that into a '65 Cuda survivor I ran across through some connections and eventually sold for 7x what I paid for it. This Duster is a bi-product of all that wheelin' and dealin'. The "inheritance" I have versus yours is a Gen 3 Hemi drivetrain/ECM, etc from a wrecked '08 Dodge Charger R/T.
You're welcome to walk this journey with me if you decide you want to make that thing a MONSTER!
The '65 "survivor" that is in another guy's talented hands now, but provided the finances after the Vmaxx sale.
Picked up this lil' gem and some 6.1L Heads to add some spice.
Voila!!! I'd say you're well ahead on the condition of the car...I need a frame rail for this one, but I didn't want a "good" car to cut into like we're planning to. We do have seats, but everything else you see missing....is !