Over kill is what is needed on the street. What you should be asking about the FWD turbos is how many of them needed that warranty. I worked there. LOTS. And, they had better rods, pistons, and valves/springs. Boost at 90°? The crank "sees" boost as soon as the intake valve is opened. Peak flow will occur about 20° after TDC on the intake stroke, depending on the cam and overlap. There should be little overlap on a turbo cam. Peak leverage is 90°. Not peak boost. Boost in the intake port (meaning from the throttle plate to the back of the intake valve) remains fairly constant once max boost is reached. And that depends on the compressor ratio of the turbo and the size of the engine. Compared to blowers, turbos are easy on parts, but they will develop much more power at the crank, becuase they use very little to drive themselves. Centrifical super chargers are next, because they are pretty limited in size and boost level, and dont place a massive amount of stress on the snout. Some, but not much. A roots type blower is rough on the snout. 6psi is nothing, especially on stock ports. Remember boost is simply the reading of resistance to air flow. So restrictive heads/ports ans small cams will show higher boosts with the same pressure supplied. Plus, that's less stress than 150hp NOS kit, and they are safe on stock cast pistons and rods.
Comparing any V8 to a modern 4 or 6 cylinder (especially import) is like comparing a B-17 to a Leer jet. The cranks in a typical Toyota(Lexus) is as high a quality as a Callies, if not nicer. The blocks are MUCH stronger, and the heads flow on average 20% more than a ported set of big block heads and feed less than 40% of the displacement. The last ported set of WRX heads I saw flowed went 320+cfm, and feed something like 141 cubic inches..(not sure on displacement...lol) I have an aquaintence who used to race blown small block Fords. He now races Nisssans. He has a naturally aspirated SE-R with the Jspec head that has made 295hp to the tires. Thats close to 325hp, from a 2.0L, with no boost. His turbo SR20 engine kept sheering off input shafts, and made close to 500hp to the tires from 2.4L.
As far as oil mods, that's up to your machinist. Find oe that does mopars. I have trouble shot engines from Mopar Engines West, and Speed-O-Motive that had power and/or bearing issues because they didnt get things right. I would find local racers who have had good experiences and find out who did thiers. Sometimes "local" just isn't worth using, and they will tell you if they needed to go further away. I drive an hour and 20 minutes to get to a shop that does the quality I need. There are many others closer.