PirateJack is just a 73+ Mopar disk conversion. It’s basically the same as what DoctorDiff will sell you with his Stage I kit, except that the PirateJack kit will be 100% Chinese parts that are the cheapest you can buy, and you’ll have almost no customer support.
DoctorDiff’s kit will come with Timken bearings, high quality parts and be supported by him personally via phone, email and even text message. Mechanically it’s the same kit, PirateJack is cheaper because it’s cheap, crappy parts. It may be cheap, but it’s not the best bang for your buck.