The problem I have seen multible times on the 4.3 GM motor breaking off the starter nosecone has to do with with the engine rocking back while the starter is being energized. This has only been seen on LP units. The fix is a electronic timer placed in line with the ign. coil that will not allow voltage to the coil untill the engine has cranked for around 1/2 second. Yuor MCFA dealer should be able to come up with the kit for this problem.