When my car arrived as a roller many years ago, the mild steel primary pipes had been Jet-Hot coated.
I installed sheets of Thermo Tec aluminized heat barrier on: the engine-side of the foot boxes, the entire under side of the transmission tunnel, and the street side of the floor.
During subsequent drives there were many times Peggy and I thought the soles of our shoes may have begun to melt.
I ducted the air from the front of car oval ports, to the foot boxes. That helped some but the level of foot box heat was still uncomfortable.
The last remedial action provided the most substantial heat relief. I wrapped the primary pipes with 2" wide Thermo Tec woven tape. What a tremendous reduction in foot box heat and a big gain in comfort.
Its probably very important that my pipes had been ceramic-coated prior to being wrapped. I've read that un-coated mild steel pipes that are wrapped are likely to prematurely deteriorate.
My pipes have been wrapped and re-wrapped several times over a period of 18 years. I last saw them bare 3 years ago. They still appear to be unaffected by the wrap. There wasn't any indication of rust. I couldn't detect evidence of metal fatigue. That's a good thing because I intend to always use header wrap.
David