My understanding is that the label balked at the last minute to issue an album called Gang Bang and as it was the last album on their contract with ABC, the band decided to call it just Passin' Thru. Apparently LP labels had already been prepared. The band liked the name and thought it was was humorous, so they used it less blatantly on their next release on Atco, Bang.
Domenic Troiano would depart soon after this to join the final line-up of The Guess Who. He would be replaced in James Gang by Tommy Bolin. Three pretty top-notch guitarists in this band, eh (Joe Walsh, Domenic Troiano, and Tommy Bolin)?
Slight oddity with the label here: the cat#, titles and everything else matches, but the LP title is given as The James Gang Bang. The band did release an LP of that title in 1973, but they had moved to Atco by that time. Anyone know what happened here? Perhaps a later issue label with a cocked-up credit?