I wouldn't sweat the minor difference in fan size or 180 verses 195 thermostats. My pontiac 400, with a 180 thermostat ran 180-185 almost 99% of the time. The temp did not go up at red lights or idling. It didn't get hot drag racing, even with 4.10 gears and #16 heads.

I worked with a man that diagnosed thermal fan clutches old school. He would drag his hand along the back side of the fan with a red rag protecting his hand. He would apply drag to the fan, on a hot engine, at idle. If the could easily stop the fan from spinning, the clutch was bad. If he couldn't, clutch was good. It sounds crazy, but he was never injured or hurt, and he was a great mechanic. There was an art to applying gradual friction to the fan in the opposite direction of the fan rotation.

Please don't try the above with a flex fan and cut your hand off. Flex fans are loud.

Your clutch has to be bad. If your pulley size was the issue, you should be able to quickly tell. Advance the idle to 1200 tmp with your foot at idle (in netraul). Is the temp still skyrocketing at idle? If it doesn't climb with the higher idle, it is the pump speed! But, I bet it still gets hot until you get a working fan clutch.