Four Winns installed a 5000 BTU ac unit in the port-side rear storage compartment of the aft cabin (queen-sized bed). The door needs to be modified or replaced to allow air flow into the ac unit to be cooled. The AC unit pan needs a drain line that runs to the shower sump to be pumped overboard. The cool air output is routed through a "y" to two 4" insulated ducts. One comes out in the front port-side corner of the aft cabin. The other duct comes out under the radio. A water pump is mounted near the front port-side corner of the engine room between the engine and the batteries. Many of the 5000 or 6000BTU units should fit in that compartment, but verify manufacturer's dimensions first.
You can find pictures of other 268s with ac installed in the sites advertising boats for sale, such as
www.boats.com,
www.boattrader.com, etc.