I had to replace the starter in my '88 Formula TPI/T5 car this weekend, so I threw the starters on a scale. FYI on below weights:

Starter removed from my car: 13.51 lbs
AutoZone stock replacement: 13.56
AutoZone repl for '96 LT1/T56: 7.73
(Both of the AutoZone units were rebuilt, not new)

I've seen others mention that a stock starter weighs ~22 lbs. Maybe some do, but not mine. The LT1 starter is definitely lighter, by almost 6 pounds.

But, the number of teeth on the LT1 starter spur gear was completely different from what I had stock, like 11 teeth versus 9. It didn't look like it was going to work, so I used the stock rebuild instead. So, I'm wondering, does the LT1 starter only work on automatic third-gen's? Or, would it have worked on my car, even though it didn't look like it?

 

Lt1 works on autos or manuals. Ive used both the fatory starter and the LT1 starter on both my automatic 700r4 and my T56.

 

OK, good to know. But, you have a T56. Is it possible that the LT1 starter does not work on 3rd-gen T5 cars? The AutoZone computer called for a different starter for my T5 car, versus an auto. So, I wondered if the stock T5 flywheel has a different number of teeth than the auto flexplate maybe.

 

A third gen T5 starter works on a T56. So it should work the other way around too. I could be wrong.

 

I am currently using an LT1 starter on an LT1/T5 combo. Works fine in my case.

edit to add: The flywheel and clutch are from the TPI 305 that the T5 was previously mated up with.

 

A SBC starter is either for a 153 or 168 tooth flywheel flexplate regardless of what trans is bolted to it.

Differences arrive ( in same tooth count starters) from the starter fitment into the different bellhousings used with various trans
In other words;
any 153 tooth starter will work on any 153 tooth flywheel while the engine is on the engine stand but may not when engine is installed to trans