The weak link in the rotating assembly is the rods, then the cast pistons. Over 550-600Hp, you had better already have aftermarket rods and forged pistons.

The valve train will also need to be addressed with better rockers, springs, pushrods, etc.

For the most part, the rest of the components can handle much more power. (Block, heads, crank, etc). Due to the journal overlap of the 429 crank, it is unbelievably strong and, properly prepped, can handle damn near 1000HP or more. Or course, if your building that kind of HP then you can probably afford better components.

How much HP a 429 can handle is very dependent on the build and componentrs used.

Paul