Did you ever figure it out? I would have asked if you had pulled the distributer cap to se if the rotor was moving when the engine cranked? I had similar and the roll pin in the distributer drive gear sheared. Mine was the original 1/8" spring pin that sheared due to the load of hyvolume
oil pump additional spring pressue on releif and cold
oil. I installed a true roll pin I got from MSD trough Summit Racing Parts( I have a Mallory System)
If you whish I could disscuse it further.