150F is not very hot, underhood temperatures can reach +200F, and coil temperature rise above that. Oil circulates with convection, epoxy does not, it is the enamel on the windings that fails, shorts windings and coil is damaged.
Modern coils have a primary resistance of about 0.5 Ohms, standard canister coil about 1.5 Ohms. Changing to modern coil in ballast system results in increased current, that may fail the ignition box. The HEI conversion eliminates the ballast, and properly control the coil charge, that is how to have a cooler, more efficient coil and ignition.
HEI conversion is not difficult, if you have electrical skills. If you want an easy to install system with support, TrailBeast of this forum sells conversion package.
