I had a ST238 on my First Day Ship 5150 PC1 (the first IBM PC) but I did swap the system board ;-)
I never did it but there was a 5 slot "AT" board that fit in the 5150 case. It was for the luggable version of the AT. (5162). That was a 286 board with the same form factor as the original PC. in the 5155 case There was also a suite of short height cards for it. By then I was running a wooden AT with a 339 board in it so I never fooled with it.