which ones, without taking it apart, are the clutch type 4.10 ratio?

how can I tell which rx7 has the the 3.90 ratio or the 4.10?

 

stock automatics are 3.90
stock 5speeds 4.10
optional 5speed 4.30 usually in gtu

 

To tell what type of diff it is, turn one wheel and watch the other. (From what I've read, someone please correct if wrong.)

Open diff = wheels turn opposite direction (one forward, one back)
Clutch diff = wheels turn same direction (both towards front or back)
Viscous diff = other wheel doesn't turn or takes a sec to move in the same direction.

 

^ i can vouch for the first two

as for gear ratio, the only way to tell is how slow the car is of the line, which 3.9 will be

 

open diff if you spin one the other one doesnt spin
and viscious will just spin in the one direction but the other wheel that your not turning wont begin to turn as fast

its not a GTU so its just a 4.10 and I know its a 5 speed stock

im debaiting if i will be swapping rear subframes or just the 5 lug swap from the car I found...

cause if I have to swap diffs its gunna be a bitch cause that was a pain in the ***.