Your trouble with the starter sounds just like the problem I had years ago with my 60 Champ engine.
When I bought this truck I had nothing but trouble with the growling noise the starter made. After alot of research and messing with bendix drives ,( I tried just about every bendix I could get) it turned out that the engine flywheel teeth weren't the same on the engine that they were suppost to be. The 245 that was in my truck was an early 50s engine and that would of been a 6 volt and the number of teeth on a 6 volt flywheel is different than a 12 volt engine. If I remember correctly a 289 V8 engine had the same amount of teeth that my 60 engine was suppost to have. I got a nos crown gear from sasco and changed that flywheel gear ....problem solved.
Maybe this will help