Re: 1850 Farm house needs new porch--Lumber to use?
T&G Southern Yellow Pine is pretty much a standard for porch floors and if properly maintained will last for years. Mine has been installed for over 25 years. Yes you should paint all sides, that will help prevent water damage.
Does the whole deck need to be replaced or do you just have some boards that need replacing? A complete tear off is often not needed. If you have a section or a board that is bad just replace that section or board. If a single board is bad cut down through the middle of the board and remove it. Slide a new board into place.
Be sure you live your life, because you are a long time dead.-Scottish Proverb