"Kimagure Dori wa Tasogare te" didn't seem to be one of Ishihara's hits so searching for its release date wasn't as easy as I'd thought it'd be. For one, I had to make sure that it wasn't a cover since Tough Guy was known to do so... in total he had covered 200 songs. With that done, it was time to check out the list of original tracks he had sung over his 31 year career... 350, includes both singles and those released in albums. Eventually, after sifting through about 20 years of his works, I found it. "Kimagure Dori wa Tasogare te" was released in September 1978, and according to the J-Wiki, it wasn't an official single, so I think it only came out in one of his albums back then. It can also be found some of his postmortem compilation albums, like "Towa no utagoe Ishihara Yujiro no Subete Vol.14" (永遠の歌声 石原裕次郎のすべて Vol.14) that was released in 2004.
The song was written by Norihiko Sugi (杉紀彦), who had also penned the lyrics for most of Tough Guy's tracks from 1978, and its music was done by renowned composer Masaaki Hirao (平尾昌晃).