There are at least three sizes:
1. Smallest-- Hitachi gear-reduction (factory 1984.5-on)
2. Slightly Larger-- Bosch gear-reduction SR97X
3. Largest-- Bosch direct-drive (factory thru early 1984)
Sorry I don't have P/Ns, but here are some photos of the largest Bosch. This one happens to be an AC-Delco remanufactured Bosch evidently. Weight is ~23 pounds, everything is big about this starter. Tight fit, was a real struggle to push it up into position, and the B+ cable terminal hole had to be enlarged slightly to fit the larger solenoid post. Fit D24T in the 740. Works great!
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The Hitachis are nice small lightweight starters but they are more susceptible to burnout, especially from extended cranking. Nobody wants to rebuild them, probably because of parts unavailibility. Most common replacement seems to be the Bosch SR97X which is more durable, slightly larger and heavier.