When I turn the car on, it cranks over with a nice grinding noise. Give it some gas and crank again, the noise goes away.

Is this normal? If not what kind of starter does my 1982 RX7 Have? because I have a '85 GSL starter that looks similar to my starter and will mount where my starter is, but the ring gear is way different.

>.> BTW I need to get rid of a GSL starter, just figured I'd say that....

 

Usually this is caused by the bendix drive failing on the starter. In rare cases the teeth on the flywheel are very worn but I have never seen this on our flywheels.
Most all of the 1st gen M/T starters are interchangeable. We have a thread somewhere that gives you this information.

 

Really? Because the starter I was going to use had way shorter wider ring gear than the stock one O.o

 

https://www.rx7club.com/1st-generation-specific-1979-1985-18/common-parts-interchangeablity-questions-630181/

 

get a 13b sixport starter. NOT from a TURBO. a regular six port. they have more torque

 

What do we need more torque for from the starter?

 

I'm not sure how it relates, but I experienced similar issues when I was having electrical problems. Replacing the battery cables seemed to fix the issue. However, my noise could be different than your noise, so I'm not sure.