KF floor pans have stiffener ribs stamped in them so I'd save all of it if it's is in good shape. The club remanufactured floor mats, however, I'm not sure if any of that run remain. If you can get yours out without it falling apart, do so. About the heater, do you mean that the heater box bolts are head in place by caged nuts that are welded to the firewall? If so, then the easiest way to pull the hearer is to remove the cover and core from under the dash and then remove the other half of the box.
If the transmission has overdrive and a round flange where the drive shaft meets, then it'll work in your Virginian (provided that it is a BW unit).
The wiper system consists of pulleys and cables and are common items found at nearly every KF vendor. If those in the parts car are good, you might as well keep them...why buy more if you need them and your parts car has good ones!
Another item to consider keeping from the parts car would be the fuel tank. If it's in good shape, it can be coated and reused. Good ro NOS tanks are not easily found...the last NOS one I saw was priced at over $200.