You can achive 350bhp and even 350rwhp on a stock 2JZ-GE engine :). This means all you would need is a turbo kit and a FMU or slightly larger injectors, appropriate fuel controller, good exhaust & intake, and bam you have a 350hp car :). So, you don't need to upgrade your headgasket, which is good, because doing the headgasket properly takes many hours of labor. The amount of boost you can run varies with turbo size and what kind of fuel control you are using. If you use a standalone EMS and have complete control of your timing curve, some folks have run ~12-13psi with a small turbo on stock headgasket. Most people with piggy back fuel controllers don't boost more than 8psi to be safe on stock headgasket. Since you have a 1997 non-vvti 2jz-ge, you don't have to change any of the engine internals since they've been proven to hold 600-700rwhp reliably and daily. Regarding suspension..prepare yourself for the worst = replacing all of your control arms + bushings, sway bars, and stock shocks/springs. This leave a nice dent in your wallet, especially after the turbo kit. Turboing sc300's is not cheap, but has been hyped as a car that is able to be turbo'd properly for cheap. It's not.