Re: Converting wood-burning stove to traditional fireplace; install new mantel
I can make not comment about making the mantel fit because you did not post a picture of it.
A couple of questions 1)Did you have the chimney inspected? 2) Is there a flue dampener in the chimney? 3) Metal flue liners usually come in sections, are you sure the metal flue liner is one piece? 4) Does the chimney have a clay liner or is it an old brick only chimney? 5)Have you considered that it may be safer and more cost effective to replace the entire chimney and fire place? 6)Was the mantel you bought made for this sizes fireplace or just a bargain, antique, or one you just liked ? 7)How old is this fireplace? 8)Are you DIYers?
More specifics are need to give you much in the way of advice.
Be sure you live your life, because you are a long time dead.-Scottish Proverb