Two-Headed Giant 2PAC follows the Pacific Old School rules with the following exceptions:
With the exception of basic lands, a player’s deck may not contain more than 2 of any individual unrestricted card counted by its English card title equivalent.
Black Lotus and Chaos Orb are unrestricted (so you can play 2 of each). If you choose to play a 2nd copy of either of card, the 2nd copy can be a "tasteful" proxy (be reasonable).
There are no sideboards.
Matches are played in teams of 2 vs 2. Each teammate brings their own legal 60-card deck and teammates take their turn simultaneously. Each team shares a single 30-point life total. All other resources (including mana) are not shared.
Matches consist of a single game. Teams are generated randomly each round based on individual win/loss record from prior rounds.