As far as the bottom ends, they are well built from the factory. They came with forged pistons, good crank, and manley rods. As long as you have a good tune and enough fuel, these bottom ends have seen 800+ rwhp. They won't last forever at that power, but it's very possible. A good safe tune and 550-600 rwhp will last awhile as long as you don't do too many back to back top end pulls. The rear diff is a 31-spline unit that is relatively strong, but with the IRS and wheel hop that can create issues with the stock half-shafts. If you beat on the car, powershifting and things like that, it's a toss up with the stock transmission. It has a 10-spline input shaft, which isn't the best for these cars. I'm sure all of the other guys will chime in and add to this, so this is all I have for now.