magnum manifolds in a early a

Exactly how close to the firewall are the manifolds? Seems like a fairly minor problem, unless I am overlooking something. What is the limitation to the thickness of added layers of insulation under the carpet. If there's not enough room between the manifolds and firewall, why not add layers of thermal insulation and sheet metal inside the passenger compartment. How big a problem is losing 3/4 to 1" of footroom??
Then there's always MR. B.F.H.!!!

BC