See where that puts you in operating temperature when you drive around. You want to be in the 195 to 205 range for a street sbc. Note that cylinder and ring wear goes DOWN as operating temperature goes up. Also, low octane gasoline burns more completely as temps go up, so you get more mileage and better performance. I think the 180 will probably be too low, given how low your operating temps are without the thermostat.
And it goes without saying you should buy a good one. Lots of after-market thermostats are crap. Why not just use the ACDelco 12TP1E High-Flow 195? (The High-Flow 180 is 12TP1D.)
Amazon.com: ACDelco 12TP1E Professional Engine...