The HP manifolds , especially the passenger side so close to the valve cover will cause the paint to burn
400-500 is fine at idle - 800-900 under normal operating
If your concerned about a lean carb condition , pull your spark plugs and look at color there
If you want to keep your factory valve covers looking pretty , try a high heat paint or install these on your exhaust manifolds
Made to protect the valve cover gaskets from heat
https://www.summitracing.com/parts/fel-ms90425/overview/make/dodge