Bruce Morse then became the group's new drummer until Ron Bushy (from a group called the Voxmen) came aboard when Morse left due to a family emergency (Bruce later returned to take Bushy's spot in the Voxmen). A booking at Bido Lito's club on the Sunset Strip soon led to regular appearances at the Galaxy Club and the Whisky a Go Go.
In early 1968, the band's debut album, Heavy, was released after signing a deal with Atco, an Atlantic Records subsidiary, the group having been signed by Atlantic's Charles Greene, who was co-producer of Heavy. All but Ingle and Bushy left the band after completing the album in the late summer of 1967. The remaining musicians, faced with the possibility of the record not being released, quickly found replacements in bassist Lee Dorman and 17-year-old guitarist Erik Brann (also known as "Erik Braunn" and "Erik Braun") and resumed touring. Brann had previously played with a band called Paper Fortress. In a 1986 interview with IB's fan club fanzine, The Butterfly Net, Brann stated that Jeff Beck, Neil Young and Michael Monarch (who would go on to join Steppenwolf) had also expressed interest in joining the group to replace Weis, but after he was chosen, Penrod and DeLoach, uncomfortable with Brann's young age and frustrated with the time it was taking for him to learn the Butterfly's set, decided to leave after Weis did.
During this time, IB were represented by the William Morris Agency, which booked all their live concerts.
DeLoach subsequently recorded with Two Guitars, Piano, Drum and Darryl, while Weis and Penrod went on to form the group Rhinoceros. In 1970 DeLoach formed Flintwhistle along with Jerry Penrod and Erik Brann; the band performed live for about a year before breaking up.