The only differences between the HK45C and the HK45CT are the threaded barrel, suppressor-height sights, and the fact the CT comes with the 10-rd extended magazines. Slide, frame, internals are all the same (assuming the same trigger variant, which can be changed anyway). Swapping the barrel is as easy as doing a normal field-strip.
You may want to confirm that you don't have a POI shift when swapping barrels; I have shot pistols in the past which would group slightly differently with one barrel vs. another. I have an HK45CT with both barrels, and they group identically. I think this is less of a concern with the HK45 series—perhaps consistent lock-up is helped by the O-ring—but confirm with your individual pistol just to be sure.
Edited to add: Of course, you should also check your shift with the suppressor attached—that almost always does change your POI.