Welcome to the team Wilson!
Cars in good condition are definitely bringing in more money, and good rust free projects from the desert southwest are getting harder to find, as the 1964 is the single most popular year for the big Impala cars.
The good news is that the restoration industry is starting to notice the 1964 model year with mostly patch panels and small trim pieces being made. But it is a start. It won't be long before you should be able to find a complete car instead of floors and rear quarters below the trim line as are available now.
There are also full aftermarket frames and suspensions with modern coil over, air bag or standard coil and separate shock being made by many chassis makers to replace or upgrade rusted out frames. They allow bigger motors and overdrive trannies to bolt in, but are not cheap.