I'm thinking about using restrictor plates in my street motor,is this a good idea or should I just install a thermostat? I want the motor to stay around 180 degrees.

No restrictor plate. I'd get a stant or milodon 180 stat, check it suspended in a pot of boiling water to see if it opens (occaisionally a new one is stuck)(work it by hand with your thumbs before you suspend it) and that it opens close to it's rated temp and I like to drill a 1/16" hole in the flat so it'll fill up wo an air pocket easier or fill it to just below the stat mounting flat then install the stat/housing

Okay, Thanks for the reply.

My brother once tried a restrictor disc and the engine never got hot enough.