That curved section in the lower left corner helps with the alignment of the new crossmember, as do a few of the mounting holes, which align with existing holes from the stock components. Or at least they should; ours were about 3/16-inch off. A call to Chassis Engineering confirmed what we suspected. Not all chassis are exactly the same. We got it as close as we could, took plenty of measurements side to side, front to back, and diagonally, and drilled new 3/8-inch holes where required, followed by opening up the misaligned holes.