Awright, lookit.
In the golden age of target shooting, a serious shooter shot at bullseyes with one hand and three or even four guns; smallbore (.22), centerfire, bigbore (.45) and service pistol (.45.)
The centerfire was usually a .38 Special revolver. There was some use of .32 S&W Long but not very much, the K32 is a scarce collector's item, and the Officer's Model Target .32 is rare. Charles Askins' little experiment with the .22 centerfire got the minimum caliber set at .32.
But the .38 revolver had a very different manual of arms than the Woodsman .22 and the 1911 .45 and people wanted to shoot three automatics for consistency and to save having to cock the revolver. (If you run-n-gunners think five shots in ten seconds is not really "rapid fire", try it at 25 yards one handed on a target with a ten ring smaller than the B zone.)
So gunsmiths like Jim Clark set about building them .38 Special autos.
Take a .38 Super, replace the barrel or at least bush and rechamber for .38 Special, accurize the gun throughout, and build a magazine that would handle five mid range wadcutters. Fine precision gunsmithing.
So the factories got in on the act. S&W adapted the action of the Model 39 to .38 Special, tightened everything up and produced the Model 52. They are finely accurate (with a great trigger, Wood.)
Colt eventually countered with the Gold Cup .38. It looks like the .45 but is mechanically different. It runs in blowback with a slight delay from a floating barrel and a grooved chamber. I don't know why they went off on that tangent, maybe they could not duplicate the Clark and similar or equal the Model 52 and keep the .38 at the same price as the .45. They never sold as well as the Model 52 and Clark kept doing conversions. Colt even provided him with parts kits for the job.
But times change, nowadays, most bullseye shooters just fire their .45 wad(cutter) guns twice. And a lot have accurized Berettas for service pistols.
Wood,
I don't know what it would take to put a .38 Special Upper on a new frame. I saw a guy chop up one of the GC .38s to make a .45 out of it and it involved some modifications. I'd want my gunsmith's opinion before I paid for the slide. Note that it will handle .38 wadcutters ONLY and only five of those. Magazines are scarce and expensive, too.