358 cubes is around 5.8L?? thats of the top of my head you can convert it using a conversion table etc
probably use carbs for regulations or just cause you dont have the issue of the sensors/computer playing up
engine longetivity depends on a few things i spose the would strip it down completly after every couple of races or race and give it a rebuild check for stress etc i dont think you would want an engine of that expense to go bang