The new foundation required engineering because the existing foundation consisted of a continuous footer of approximately 4" x 16" and a 6" block wall that did not have the cores filled. I'm always amazed when I see how houses were constructed many years ago and consider the myrid of changes that have occured over the years in order to build a better house, unfortunately it also means a more expensive house.
With engineering we had to dig pier pads around the house, digging under the existing footer and below the frost line, that was reinforced as a column was formed over each pad, all cores were poured solid and a continuous bond beam with rebar was formed around the entire block perimeter. Part of the old wall was torn down because it was not level or plumb and replaced with a poured concrete wall.