Is this the issue you mean, Snarf? (JSA 29)
I haven't read that one.
While I often like the art in the JSA series, Geoff Johns' writing really isn't my style. I read a trade of JSA stories with Hawkman and Black Adam, where the JSA went back in time to Ancient Egypt, where they were inadvertantly the inspiration for ancient mythology of the Egyptians. It had some interesting ideas, but it drifted a lot into less engaging storytelling, and overall was disappointing.
But maybe I'd like the story you list more. If I can find a trade or the issues you mention with Solomon Grundy, I'll give them a look.
Solomon Grundy is a mysterious and Halloween-festive character.
In the recent past, I liked a 2002 Elseworlds GREEN LANTERN: BRIGHTEST DAY, BLACKEST NIGHT one-shot, by Steven Seagle and John K. Snyder.
Despite being a modern-age story, it was very true to the style of a 40's Green Lantern story, with fantastic art by J K Snyder. And Grundy was handled well also. In all his Frankenstein-esque glory.
I also love Solomon Grundy's origin, which I first read reprinted in WANTED # 4, back in 1972:
