A 1969 Polara 2dr hardtop just went up for sale in Florida three days ago -- see here. From the ad: "383 motor car needs restoration but that 383 is nice (...)" Given the condition, it seems somewhat overpriced at $4.5k, but it has all the special 500 trim intact (AFAICT) and it sports a...
www.forcbodiesonly.com
I hope it is not too late, as the seller seemed pretty desperate when I communicated with his friend who'd listed it for him. It may be too rusted out to save DM23G9R209590, but all the trim you need seems to be there. The price was too high to start with, but it went down from $4k to $2.5k a few days ago and my guess is that $1.5k would take the car.
PS: your car is a fuselage C-body, not a slab-side one.