The W58 lasting under boost really depends on how it is driven but once you add boost you'll definitely stress it beyond what it was designed to reliably hold. Instead of 400whp, try 300whp. Really it's torque you should be more concerned about so keep in mind the W58's design wasn't even intended for even as much torque as a *stock* 2JZGTE engine (about 310ft-lbs crank). It's also the immediacy of the torque a turbo has.
I have an ACT-HDSS clutch in mine which is nice and built for 278ft-lbs max. That's good for stock 1JZ power. You could try the ACT-XTSS for more holding power but it's going to be a matter of time with a W58 even with only 80k miles.
For flywheels, I'd honestly leave it stock if you have no turbo unless you live in very flat country.
1993 SC300 5-speed NA | Built R154 | Gixxer_Drew Susp. 600/325 | TT: brakes FR, rims, rear sway, seats | Koyo rad | 4.272 TT Torsen LSD