Dont cheap out on a junk kit. If you want a 393, dont use stock rods and 302 pistons! Stock rods suck at 500hp and the 302 pistons will need the skirts cut. Do buy I or H beam rods, and get the correct pistons, cast cranks will be fine for 500hp. A chevy rod journal size is a plus, as there is more rod size verity out there to choose from to get the perfect comp height.

For a 408+ci you should fine a crank that uses chevy sized rod journals to free up extra clearence for the rotating assembly and to prevent cam clearence issues with monster cam lobes, you still need to grind the block but not near as much as using the standard ford rod journal. Plus, with the chevy journal the crank will weight less and balance easier with the 28oz instead of using the heavier 50oz stuff.