I have one action that I use for both a carbine and a handgun. That may not technically be legal but I doubt any LEO is going to make issue out of it unless you have robbed a bank or committed some other crime with the firearm. Then it may end up as one more little charge they stack onto the pile. At that point you got bigger problems anyway.
I don't loose sleep at night worrying about whether an officer is going to take my serial number and contact TC to find out how the gun was originally configured.
I put this in the same category as folding stock on a rifle shotgun. Isn't that technically configuring a rifle as a long barrel pistol? As long as your legal to own both a long gun and a hand gun I personally wouldn't worry about it.
Ray