To build a 472 you use a 30 over 409 block or larger, if you can not find one to clean up to that figure. You take a 454 crank that has a minor journal blemish that won't clean up at 20 under (your machine shop should have one or two stacked against the wall as they always turn up) and turn it down to standard 409 journal size on the mains (and hopefully no more than 10 under on the rods). This is combined with standard length stock big block rods, or some longer aftermarket rods (a lot of 472 pistons use long rods), and a set of new pistons from Mahl, JE, or Diamond to make your short block. Top it off with a set of Edelbrock aluminum 409 heads painted Chevy orange and you have the basis for a great rat rod motor or one for your Impala.
I just wish I knew that a BBC crank fit inside a 409 block back in the mid sixties when I had both motors in my garage. I might still be running W motors today instead of 4.600 bore BBC motors as I do now. I think the older W motor had a lot more charisma, if not the raw potential of the Mark IV BBC.
Just keep in mind if you use a truck block (there are a lot more 409 blocks surviving as truck blocks than as car blocks) to increase the static compression to compensate for those big chunks missing out of the top of the bore on a truck block that are not machined into a car block.