There are quite a few 1A2 folks here who can assist you through this transition. It is not as complicated as it seems. Partner only needs two dedicated pairs per station and you have plenty to work with, so you are in good shape. I assure you that the existing wiring that you have is better than any new wiring that could be provided. Quality standards are much lower today than back then.
It's midnight here, so we'll have to discuss this tomorrow or at a later date. You've come to the right place for support on this project.
