If you seriously want to backbore and lap the bores. Please send them to a professional. Dean Harris at Skeets in OK would be a great choice. He will tell you what can and cant be done, do it right, and likely cost a couple hundred per tube.

If the wall thickness is there to be able to backbore, then the pitting is just a cosmetic issue. You could save a lot of money and just leave it be.

Dudleys advise is spot on and the same advise I was going to give you.
The barrels are the heart of the gun. A guy with 40+ years of experience doing barrels and with all of the right equipment is the way to go.

Thanks for the advise gentlemen.

Good luck with your project!

If you need them shiny, just polish them with abrasive paper. We have seen many guns ruined by people who could not leave them well enough alone.