So i got a 86 rx-7 with a swapped engine. Im pretty shure its a 89-92 turbo II engine, by looking at the intercooler and water fill neck.
But how can i look at the drivetrain, suspenson and brakes to see if they are from the 86 car, or from the turbo car where the engine came from?

 

It doesn't really matter. There are only a few minor differences. S5 (89+) uses plastic sway bar end links and integrated ball joints. That's about the only difference.

 

For the drivetrain, a turbo transmission will have a removeable cover on the bottom, while an NA does not. And a turbo LSD rear-end will have a tag that says it is limited slip & it will have 11 "ribs" on the case (vs. 9 NA).