If you don't have much in it, then make it into what you want. I have two guns with Hamilton Bowen right now being worked over. One will be a 5-screw K frame Target with 8 3/8" barrel chambered for the new .327 Federal Magnum.
As to deciding between ACP and LC, there are a lot more Smiths in ACP, so I would go with LC to be different. LC will be a lot less work, since the headspace is the same as the 28 is already. ACP will take a lot more machining.
I've got a 1917 frame I fitted with a spare .45 LC cylinder to make a convertible. It works great, but you have slop when the cylinder is open due to the location of the frame lug. If you fitted the 28 for ACP, you would have the same slop unless you replace the frame lug.
Chris