I asked this question on 3rd gen and no one seems to know. It's just 'I know a guy this and that'. I want to hear from a person who actually done this. I'm building a ~600hp FD and need to know what tranny-clutch I need. I already bought a Exedy twin plate for the FD so it would be nice if I could still use it. Thanks.

 

The stock tranny should be able to handle 600HP with a good clutch, but your rear end will need to be upgraded.

 

If you take a look at the street classes in drag racing, you will notice that the RX-7's seem to be able to get by on the stock transmission while making 600-650 whp.

I'd say this is the brink of breaking... living on the edge so to say. Like Icemastr said, clutch, rear end, axles, etc all need upgraded.
This isn't done on old used transmissions either.

 

Thanks. I will be upgrading the diff and the axles. I guess I'll stick with the stock tranny until it goes. I'm not going to be hard launching day in and day out. Just once in a while.

 

Scatter shields are good too.