I know for Cobras, never looked at 427 Cobras or 289 Sports.
A thin walled molded rubber boot was used on Cobras. They often did not last long because the cut ends of prop rod tubes were often sharp and or had a sharp cut off burr.
We were unsuccessful in finding anything that was an exact match. At the time, about three years ago, tooling cost estimates to have a mold made was prohibitive to make parts for just four of our cars.
