I personally wouldn't do anything that can't be "undone" later to any rare car. Keep the modifications to basic bolt-ons, and keep the original parts.
Personally, I like coupes better, especially for a PT car, so I would start with that one
I bought my '69 malibu for $500 as a rusty driver car with an excellent interior. I'll never restore a rusty car again
...way too much work.