Does the starter bolt to the engine block, or the bellhousing? On the block-mounted starters, there are a special set of mounting bolts with knurled spots that are supposed to create a very close fit between ther starter and the bolts. If someone has installed the starter using regular 3/8" standard bolts, there's too much room for movement. Also, be sure the back end of the starter housing has the reinforcement bracket attached to it from one of the through-bolts to a bolt hole just below the cylinder head. Another approach would be to get one of the lightweight gear-reduction starters we used on round track race cars.
Jerry
