Mike, try Perogie Enterprises in New Jersey. Pricey, but always correct. and if he does not have it, he can certainly locate it!!- Dave
If by heat riser you are refering to the tube that runs from the exaust manifold to the choke on the front carb. You can get the entire kit from Jim Cowles Shelby parts and restoration WI. The kit comes complete with both lines and insulation covering for the tube less the fresh air filter that you will have to make. Dominic