I pulled up the carpet of my stick built 1949 home and found plywood patches, apparently from a water issue decades ago. After removing the patches, I cut and installed recycled and new tongue and groove oak slats. I've never fixed a hardwood floor in my life, but dived in anyway. I had to cut out slats to keep the lay of the staggered slats, so they would blend in. The floor came out pretty good but the newer slats didn't stain the same and stand out. Its in an area that has a round rug so not noticeable at all. Most of it blends in.