1979 Chevy Truck hot exhaust

Engine Mechanical problem
1979 Chevy Truck V8 Four Wheel Drive Automatic

truck had a new crate moter when I got it but had burnt valves in #2 cylinder had valves replaced and heads resurfaced, now exhaust is very hot, also replaced cat converter and exhaust system. New cat smells like sulfer bad, truck not getting hot but exhaust is. Is it timing? Or carboration? What else can cause the high temp? I think this it what caused the valve problem in the first place. Thank you.