engine sawp a v6 to a inline 4

What is your question?

i was wanting to know how hard would it be to, swap a v6 for a i4, and what size will work, i'm looking to swap because the motor in it has a blown and, to save gas put a i4 if that would be any gains on fuel economy, if i'm not mistaken it is a si accord, and any ideas on where to find one on the east coast near north carolina