Probably best to get them powder coated. Could try so high temp paint from autozone or something if you want it done cheaper. That's all I can think of.
I google'd this same topic last week. I was surprised to see that ALOT of the higher end cars on the different forums were using high heat barbecue grill paint.
Plasti-Dip will work and like Blk2015GT said it will be nice to see it and be able to take it off if you dont like it or sometime down the road want to go back to chrome.