Welcome aboard Ken, and thanks for saving a Seafari, one of the more rare but most versatile of all SeaCraft models! Big is right, you have a '72 or earlier model, but my guess is that it's a '72 if you have the load capacity sticker under the helm. 73 and later models had the sticker below the helm. Mine is evidently an early '72, because it has the sticker on the port side of the cockpit, just aft of the cabin bulkhead and below the teak trimmed shelf.
Regarding the new synthetic core materials, check out surveyor
Dave Pascoe's thoughts on the subject! There is little test data on the newer materials; he likes end grain balsa core because it has much higher shear strength than the foams, and unlike the foams which don't naturally absorb resin, it wicks resin into the grain, so it bonds very well to fiberglass!
When you're looking over the boat for damage, there is one area on a Seafari that should be checked. There is a small bulkhead just forward of the head location (forward of the hinged lid between the bunks. That bulkhead is tabbed to the inner stringers with some heavy (~24 oz) woven roving, and if the boat was run hard in rough seas, sometimes that tabbing will come loose.
Good luck with your restoration and post some pics, which tend to stimulate ideas and suggestions from this gang!