I'm getting close to assembling my 273 4 bbl for my '65 Barracuda FS project. Been studying photos of like engines and noticed some have heat shields installed between the driver's side exhaust manifold and the spark plugs, and some don't. My project did not come with these shields and am wondering if they were installed on all 273s from the factory and mine are just missing, or maybe not all 273's got them. I looked at the parts book and can't find them listed. Are these being reproduced?