i think the AFB/AVS is more problematic because the fuel is closer to the manifold center. Also they are aluminum body's and get hotter than the holley.
Had a look at this. A356 has an almost 60% higher Thermal Conduction rate than does Zamak (Zinc based alloy most likely close to what Holleys are made of). Zamak: 729 BTU-in/hr-ft²-°F A356 (Perm Mold Cast): 1160 BTU-in/hr-ft²-°F