How much progress had Van Halen made on their seventh studio album before parting ways with David Lee Roth in 1985, and how much of that work made its way onto 5150, the band’s first album with singer Sammy Hagar? Naturally, it depends who you ask. Nobody disputes that the band’s original lineup had begun writing some songs for the follow-up to 1984’s smash hit 1984 before personality conflicts and a dispute over Roth’s 1985 covers EP Crazy From the Heat led to the singer’s departure. The band recruited Hagar, fresh off his own platinum sales success with VOA and the hit single “I Can’t Drive …