There's really only 2 starters for the SBC/BBC, and the size of the flywheel or flexplate dictates the choice. The starter for use with the 153 teeth flywheel/flex plate has the 2 mounting bolts straight across from each other. The starter for use with the 168 teeth flywheel/flexplate has the 2 mounting bolts staggered, not in line. The TH350 should use the first combination.

Bob