Heat isn't a problem unless the guage reads hot... it sounds like you're saying it just feels hot. A healthy engine will generally run between 175-195 degrees F, hot enough to burn your hand. Changing the header and cams will have little significant impact on the engine's operating temperature, the valve cover absolutely none.

If you are worried about it, swap in a 94+ Integra or del Sol radiator. Much cheaper then a Fluidyne, not to mention the Fluidyne is overkill for just a B18C.