Could you elaborate on the "risky" bit please, are we talking, too much stress on engine, driveline components etc
Not so much to much stress but MORE of course. If it`s not tuned properly it`s not likely to last 5 minutes. You also need to factor in other upgrades such as suspension, tyres, brakes. Making a stock 350z pushout 400+ hp is ok but if you actually want to drive it all the previously mentioned parts are a MUST,
I have done 5 Rx7's buddy, so know the pitfalls and extras that are never considered over and above the engine work.
A curious question but any thoughts and views on whether the auto box would be able to withstand the same 400bhp ish mark. It may seem odd but i have my reasons, its not set it stone that i want an auto however