I have used the thermo-tech insulating material with good results in tight places. I bought it from Summit. I too have a fuel line that is close to a header tube and my exhaust is very tight to the floor in some places. I used their line wrap for the fuel line and self adhesive sheeting for the floor areas. They claim to reflect a significant percentage of the heat.
69 RS Conv therapy program, Autogear M22, 8-pt cage, with a new 410! SOLD
New therapy program - 68 Coupe. Will be survivor exterior, modern underpinnings! SOLD
67 Belair with perfect floors, pinchwelds and firewall. Hmmm!