Technically, seven Golden Age heroes appeared here. Editor Schwartz had re-introduced the Golden Age Flash in the classic "Flash of Two Worlds" story in FLASH #123, and a follow-up in FLASH #137 strongly intimated the possibility of re-introducing other members of the Justice Society, though they only appeared more-or-less off-panel. Both Golden and Silver Age versions of the Flash are also in this JLA story, but the villains capture both of the super-speedsters and keep them sequestered for the majority of the tale.
The selection of "older heroes" is interesting; apparently Schwartz and writer Gardner Fox weren't worried about taxing any young brains by bringing in the 1940s versions of Hawkman, the Atom and Green Lantern as well as the earlier Flash. The Silver Age Hawkman doesn't meet his predecessor, but the Atom and Green Lantern of the 1960s do. Oddly, on the first page of the story where the Society appears together, Doctor Fate notes that other members of their august group have sent their good wishes even though JSA rules prevented their attending. Among the names of the non-attending is the Golden Age Wonder Woman. Perhaps Fox merely wanted to suggest that the other Wonder Woman had a distinct history with the JSA that did not impinge the career of the heroine currently appearing in JLA, but as I recall the Earth-II version of the Amazon Princess never appears in a Gardner Fox tale. No mention is made, though, of the existence of an Earth-II Batman and Superman, though the 1940s versions of those characters also made occasional JSA appearances.
The story is essentially a chess-game involving the two teams of heroes against two teams of villains from each of the two Earths: Chronos, Felix Faust and Doctor Alchemy from Earth-I; the Fiddler, the Wizard and the Icicle from Earth-II. First the villains challenge the heroes to prevent assorted robberies, and the heroes of both worlds are temporarily flummoxed. The villains then attempt to elude pursuit by going to one another's worlds with their ill-gotten gains. However, in the narrative's most amusing moment, at least some of the villains can't help wanting to plunder the rich again, even though they don't need money. This leads to an involved plot to confine the Justice League to their own HQ with a magic spell, a plot which can only be circumvented when the heroes of two worlds switch worlds to combat their regular foes. It's a typical Gardner Fox story, with nearly no character-moments but lots of heavy verbiage and rapid transformations of characters and things.
I find it unlikely that Schwartz had any plans to reviving either the Justice Society as a whole or any of the members who already had Silver Age doppelgangers being published by DC. However, Schwartz did feature four of the JSA heroes in "tryout" episodes of THE BRAVE AND THE BOLD feature, teaming up Black Canary with Starman (mentioned as one of the no-shows), and Doctor Fate with Hourman. However, none of the 1940s characters received an ongoing series until the Justice Society itself was revived in 1976.