Indy's SR heads require the use of Indy's 440-10 external oil line kit for rocker arms. To assure adequate top-side oiling, the external feeds run from the gallery plugs at the rear of the engine to the cylinder heads and then to the rocker shafts. Stock Mopar heads oil between the ports to the rocker shafts. Indy chooses to move the passage to the outside in order to gain a larger port cross section. Thus, airflow increases when the passages are eliminated.