It may not be "period correct" but I finally decided to replace the push-button safety on my new manufacture Inland 1944 model. Let's face it, the gun isn't likely to suddenly shoot up in value during my lifetime, and quite frankly I value it more as a shooter than trying to keep it exactly as it came from the factory. Not that I plan to do any other changes, but that push-button safety kind of sucks! When reaching for the mag release it's all too easy to push the safety to "fire" which could cause a NG in the wrong hands. Also, it's just plain irritating. By going to a flip safety when my index finger samples the safety on its way forward, the different contour with be instantly noticed and even with pressure applied it can't pop over to the fire position.
Hold onto the safety and keep it secure. If it's original to your carbine it does add to the value of it. Using a flip safety is understandable and does help, of that there is no question. As to value. Original carbines have been jumping up again in value. Now rebuilt carbines are selling in the $900 to $1000 range if in good condition.