Although I have always liked the Cal, a re-power alone may end up costing more than a whole boat with a working motor. The cost to the prior owner to re-power my boat was twice the asking price of the boat you are looking at. My boat is about the same size and age and came originally with a A4 or Ferrymann diesel. For comparison here is one in my area that has been on the marked for a while, with a working diesel,
Cal 2-27 Sailboat
If you go with the outboard you will come out ahead for a time, but if the long term plan is to work out some type of inboard power you might be in for a pretty big total investment compared to a ready to go boat. That may not be a bad thing if you have the $, love the boat, and have the time and skill to get it done.