With a .060 4.19 bore and 4.25 stroke you get 469 CU. Just fudge it to 470".
On the 482" same thing. Ad says forged crank so my guess it's the 4.375 RPM crank with a .060 4.19 bore and there's your 482" out of a 428 block.
I have no idea how he's using the 2.25 and 1.72 valves and getting them to work.
My simple guess............