...Going to need to learn or find someone that know how to replace panels so they look like they have never been touched. In ways its unfortunate that the prior owner cut out the old panels - guessing they were not included with the car for at least their dates. Depending on just how much you got with the car (parts) you might consider looking for a late 67 San Jose coupe as a parts car...
I would STRONGLY suggest this approach if you intend to "restore" this example to anything beyond the typical "rust-belt" full-floor, cowl and quarter panel rebuild job. Certainly, a person could section in the whole floor pans with reproduction parts and many people are quite capable of making it look good enough for the local Hamburger/Malt Shop car shows. Perhaps, this is the compromise you are willing to accept on your project and if so, just keep in mind that some (judges) might easily detect this at a more stringent venue. Getting the unibody "right" isn't very easy for even the most skilled auto body persons because it is nearly impossible to duplicate (or simulate) the factory welds.
There are threads discussing how to section in panels and re-using the original welds (by re-using the larger portions of the original panels where they are still good) but your pictures, showing they have been cut out and presumably already thrown out, limit your options on this detail.
A "Donor" California or Arizona Coupe could supply you with enough "original panels" to save you a whole lot of grief. Most of the "convertible only" panels are likely intact on your car and those parts could be grafted into a better job with that coupe body. Jeff's advise is very good on this detail.
