Finding old timber that is as similar as possible is probably the best approach. Then the best tip is Blocket and some patience. On the other hand, the floor looks fairly fresh, probably because the carpet protected it, so complementing with a new floor might not be too bad. It's impossible to say for sure from the picture, but I think it looks like spruce. I don't see any planks with the reddish core that pine has (but it could also just be sapwood).
Moreover, I would advise against lye washing the floor. Lye makes the floor soft and sensitive (in practice, it corrodes the wood). As a building conservator, I would recommend soap cleaning instead, even if it might not be liked by everyone. However, it is a simple method that leaves all other options open (oil, varnish, etc.) if one gets tired of it; going in the opposite direction, however, doesn't work.