Adventure Comics #40 (Sandman vs. Tarantula)

Adventure Comics #44 (Sandman vs. the Face)

Adventure Comics #47 (Sandman vs. the Lady in Evening Clothes)

Adventure Comics #56 (Dian Belmont in drag as Sandman)

All-American Comics #25-27 (at least one Hop Harrigan story in which he appears as Guardian Angel)

Captain Marvel encounters the future CapMarv

"Captain Marvel Jnr. Meets Himself in the Future"

Crack Comics #31 ("Ike & Dooit" humor strip by Cole)

Golden Age (fanzine) #7 ("Mnemo, Son of Litle Nemo, in Nostalgi")

Hit Comics #26 (Kid Eternity summons Plastic Man)

Hit Comics #32 (Kid Eternity summons Blackhawk)

"Mr. Mystic" story in which he encounters the Spirit and Lady Luck

Plastic Man #21 (vs. Amorpho)

"Weird World" from Marvel Super Action #1 and Marvel Preview #1

Whiz Comics crossovers between Captain Marvel/Golden Arrow/others