Toyomoto does N/A to turbo conversions. If you're looking for BPU or BPU+ hp levels, I'd suggest the Toyomoto kit... SoundPerformance can make a kit as well. As long as you don't need 700rwhp, this is a good option. If you're going for huge power, the TT is the only way to go as the NA drivetrain is no good above 400-500rwhp. (small clutch, no LSD, weaker axles, etc.)
Parts for 425rwhp are around $7k to $10k depending on configuration. At intermediate power levels, the overall costs for TT v.s. NA come out pretty close to equal. For my investment ($11k for car, $8k in speed mods - around $21k total) I've never had any problems beating any local BPU Supras in either street, track or dyno areas.
As mentioned, the main drawbacks to the NA are the drivetrain, which will hinder off the line performance through a small clutch and open-diff... You can expect 2.1 - 2.3 60 ft times with this setup. The clutch won't slip when you want it to and will grip when you want it to slip. Either way, you're gonna spin tires badly. As far as the engine is concerned, I find that the NA with the turbo behaves better than a TT BPU... With the higher compression (10:1), it has much more grunt down low when the turbo isn't working, doesn't have the 1-2 turbo hesitation, and has a generally wider, smoother power band. The 10:1 limits boost pressure due to detonation, but the engine is more powerful without the turbo, so it ends up being a wash. 10:1 will also cause your turbo to spool faster.
As far as engine strength is concerned the 2JZGE is almost as sturdy as the GTE. Toyomoto has built many turbos around the GE with 600+ at the wheels.
The link in my signature has details of the turbo setup.
