I just bought a 355 for my car and it came with a ministarter for an 87 camaro with a 5 speed. My TA is auto and I am using the stock flywheel. Will my mini starter from the 5 speed work with my flywheel or should I stick with my old starter?

The difference between a flexplate and a flywheel doesn't matter (auto vs. manual). It's the diameter of the ring gear around the outside that matters. 3rd gen V8s all came with the smaller 153 tooth sized flexplates/flywheels to my knowlege. If the starter that came with the new motor is designed to work with this sized flywheel/flexplate it will work. If it's designed for the larger 168 tooth units it will not.

I think when they made the switch up in 86ish from the 2 pc rear main to the 1 pc rear main, they also switched the teeth count on the flex/fly's.

If you want, just measure the diameter of the flywheel and the flexplate. If they are the same, it's a direct swap over (just be sure to check clearance and shim as needed).

Too bad the engine didn't come with the flexplate...
I have a starter pulled from my car before the engine swap, so I know for a fact it will work. I'll try comparing the gears on the two starters.

It's not the gears, it's the overall mounting location of the starter. STOCK starters it's easy to tell: "straight" bolt pattern starters (2 unequal length bolts on exactly opposite sides of the starter) always used to go with smaller 153 tooth flexplates. "Staggered" bolt pattern starters (2 equal length bolts offset a few inches from eachother on opposite sides of the starter) always went with larger 168 tooth flexplates. Simple simple.

However, aftermarket mini starters are a different bag. They can have either bolt pattern and fit either size flexplate/flywheel. No way to look at one and say- that goes with XXX tooth flywheels/flexplates. Best bet with things like that is to get any numbers off the outside of the starter you can find and get in touch with the manufacturer.

Will do. Thanks.

Most fit both. Does your starter have 4 holes drilled in the mounting surface? If it does it fits either.