Installing temp guage sensor(aftermarket)

Thermostat cover with fitting option? I like that better than drilling. Where might I find?
Soon as I get one I'll get a new t-stat. Odometer says 93,000, by the way.
I tried pulling the inst cluster today. Finally decided maybe I'll just focus on getting my new gauge sensor mounted for right now. That's a tight little area behind that dash. Everything but the temp still works and the gas gauge reads accurate below 1/2 tank so I'm leaving well enough alone.
A friend adjusted the carb for me and it runs a lot better. He said I had it idled down too low and was running too rich. Now it's holding a steady 45lbs oil pressure even at a red light and he smoothed it out a lot. It had been idling rough. That clatter does sound like ignition ping but I don't understand why it only does it after I've ran the car for a while.
Back off the timing. Turn distributor clockwise or counter?