Given the high ceilings, your location and the low R rating of the insulation, I would estimate the tonnage at about 400 square feet per ton or about 16.5 tons of cooling total. But for sure get a professional estimate.
YMMV
:beer:
Edit: FYI, 1 ton = 12,000 BTU
JB.........WELL DONE!! Stunning find! I'm very happy for you that you landed solidly on your feet. I bet you feel a little tingly every time you come home from work on that long commute and see that home!
Again, well done! :thumbup:
:beer: