Ashcan Copy: Flash Comics, the title that introduced Captain Marvel (then called Captain Thunder). Whiz Comics #2 was the first actual issue; #1 was an ashcan edition and was never publicly released.
What Could Have Been: According to Alex Ross's Rough Justice art book, he proposed a redesign of the Marvel Family which would've slightly aged Billy to that of a teenager, and modeled him and Captain Marvel after their counterparts from the TV show. Ross's revision would've also included a reworking of Vulcan, the Expy of Black Lightning from Superfriends, with a backstory connected to Shazam. This direction was pitched when DC's decision to make Freddie Freeman inheritor of Shazam's power had been decided on.