6 bolt posi

[1964C10]

First thanks all for making this such a great site! I have found more answers here then anyyyywhere else, and some cool rides and ideas as well. On to my question, I did a lot of searching here but I am still confused. I have a 64 stock 12 bolt non-posi with 6 lugs. I am planning on keeping the 6 lug but have been thinking about upgrading to a posi, in order to do this, do I need to swap out my complete rear end or can I keep my axles, housing etc? Furthermore, I understand the benefit of positraction but I am planning on making this a daily driver with just a streetable ~350-400 hp fuel injected engine so is a posi really necessary? Thanks again all!!!