“These are the best days of our lives” … because TMZ has learned the brand-new cast for Season 12 of “Vanderpump Rules” will begin filming in a few weeks.

Production sources tell us … the rebooted Bravo series will go into production in early April. We’re told the cast is made up of 14 members … some will be full-time and others will be friends of the cast.

We’re told the rebooted version of the long-running series will keep its original formula, which will take viewers inside the hookups, feuds and drama surrounding Lisa Vanderpump‘s West Hollywood restaurant, SUR. We’re told the SUR-vers’ homes and lives outside the restaurant will be the meat of the show.

Our sources say the incoming new cast members finalized their contracts last week.

As we reported … the network told us in November LVP would return for a new season, but would be surrounded by a new cast.

TMZ broke the story … most of the OG cast members weren’t too surprised by the new direction when they were informed of the decision … especially after the show was put on pause back in April.