I have always used white lube on all my assemblies and have never had a problem, a tube last me a long time. I have never had any luck with high temp paint on headers, but some claim to have over the years, prep would probably be the key, ceramic or powder coated manifolds-although tough in your set up. Blocking off the heat riser will make it harder for the choke to work on cold starts, depending on your locale that may or maynot be a concern, you would be better off leaving it functional and adding a cool can in the fuel line or a 1 inch spacer, I block mine off most of the time but I'm in Florida. There are other views and maybe this will bring them out for you.