"Doing it right" involves placing the plate onto the back side of the pump with no gasket, then using a hammer or other suitable "beating tool" to gently work the plate until it just barely touches the impeller all the way around. Then when you reinstall the plate with the gasket, the clearance will be correct.
When I first put my engine together, I didn't do that. Sitting in a closed garage and idling, even with the big aluminum radiator and twin fans I have, the temp would creep up over 200, 210. I remembered I hadn't clearanced the plate and made sure I did that the next time I had a reason to pull the pump. Now, running down the highway in the Texas summer with the A/C running flat out - it rarely reaches 180.
It makes a BIG difference.