Exhaust gas heats the manifold quicker and gets hotter as well. When the engine needs manifold heat the worst is right after startup- - - -when the coolant is ambient temperature. Find a piece of 1" aluminum plate and some 5/8" OD copper tubing, plus a couple of compression fittings, and make your own heat plate. There's no sense in paying someone an outrageous amount to drill a few holes!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!