Tim,Have the block bored and squared up,then do a mock up and measure the deck height.Once you determine that,then have the deck milled enough to get the piston to zero deck height.The stock 409 rod length is 6.09,the stock rod length for the big block is 6.135.The 6.385 rod is an aftermarket improvement,much like the 6.0 inch rod for a small block.The price for the 6.135 and the 6.385 is in most cases the same.The 817 head is a really good choice for what you're wanting to accomplish.The 409 length rod and the stock stroke 348 piston will give you a bit more compression,but the torque will be peaky.The longer rod,and the 7815 piston will have a bit less compression,is lighter,and has a broader torque curve,which is better suited in a street car for driving pleasure.