First, welcome to N.E.!
You have certainly come to the right place.
As for your 8 with the dented muzzles, are you first proposing to cut the barrels back and give them a go with roundballs?
I think that is what I would do. Heck, even Holland and Holland built some smoothbore 8s and they shoot quite well from what I have read.
I am sure some more knowledgeable folks than I will be along soon to help you out.