I don't think the M20x1.5 + the angle fitting will fit. The clearance between the hood and the top of the thermostat is pretty limited. It might though, worth a shot if you can return the parts.
I messed with the thermostat spring. I am not convinced it does much with a stock oil cooler. A larger unit or two units might be a different story.
No need for another thermostat unless you make a plate like the Stett plate which removes the stock thermostat.
I really want to stop by XRP
and see if they have any fittings that may work.