Running a Magnum block does not mean you must run Magnum heads. You can run LA heads. If the Magnum is an early block and has LA oiling drilled, just install LA cam bearings and LA based camshaft to oil through the heads and rocker shaft. If the Magnum block is not drilled for LA oiling, you can still use LA heads with a rocker arm that allows pushrod oiling, like Comp Cams Ultra Pro Magnum and clones. This is how the Trick Flow 190 head works on the Magnum block with the correct Harland Sharp rocker srms.