Not sure on what Colt frames are named, but the S&W J frame is a stretched version on the S&W I frame. A longer cylinder was needed to fit .38 Special rounds so S&W lengthened their I frame to accomodate one.
In between the I frame and J frame was the Modified I frame. I don't think it had the longer cylinder, but I am not sure.
Also, I believe the J frame's cylinder was lengthened slightly with the introduction of .357 mag chamberings for this size. I believe it is referred to as a J Magnum frame.
Colt did something similar with their Police Positive. To use the longer .38 Special and .32-20 rounds, they had to create the PPS which is a stretched frame version of the PP.