Cover letters credit confirmed by Todd Klein in The Danny Crespi Files Part 12, posted 23 June 2017 on his blog (Todd Klein's Blog at Goodreads).
New splash page by Dave Cockrum and Joe Sinnott. Story pages 2-5 reprint "Marvel Boy and the Lost World". Page 4, minus panel 1 and panels 2 and 3 are expanded and re-captioned. Pages 5-7 from Marvel Boy (Marvel, 1950 series) #1 (December 1950).
Story pages 6, Panel 1 and 2 are re-captioned from "Eyes of Death" Page 3, Panels 6 and 7 from Marvel Boy (Marvel, 1950 series) #1 (December 1950).
Story page 6, panel 3 is expanded and re-captioned from "Murder by Magic". Page 2, Panel 3 is from Astonishing (Marvel, 1951 series) #6 (October 1951).
Story pages 6, panels 4 to 6 are from "Caves of Doom". Page 2, panel 4 to 6 is from Astonishing (Marvel, 1951 series) #5 (August 1951).
Story pages 7-12 are from "Caves of Doom". Pages 3-8 are from Astonishing (Marvel, 1951 series) #5 (August 1951).
Reprint notes the original publication on the splash page. However, it states it is from Astonishing Tales #5 which is incorrect and should state Astonishing #5.