Urethane-insulated motor mounts in a Pantera are a bad idea. The heat coming off the headers will melt the urethane normally used, especially on the left side. Hall used to sell them and I've helped chisel a couple of mounts apart after open track events. The left side is particularly troublesome because the left mount needs to be taken apart in order to remove it from around the shift shaft. But when the urethane melts and flows like pudding around all the parts, the mount-halves cannot be easily separated. So you're left chiseling and hacking melted-and-resolidified urethane off while its under the header and behind the shift rod. No oxyacetylene torch was available or I'd have used it! I suggest synthetic rubber mount insulators. Urethane might work for Mustangs with different around-engine air flows but not Panteras. It does work on ZF mounts since the heat is far less there.